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16 article(s) from Reissig, Hans-Ulrich

The LANCA three-component reaction to highly substituted β-ketoenamides – versatile intermediates for the synthesis of functionalized pyridine, pyrimidine, oxazole and quinoxaline derivatives

Tilman Lechel,
Roopender Kumar,
Mrinal K. Bera,
Reinhold Zimmer and
Hans-Ulrich Reissig

Review
Published 13 Mar 2019

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1. Graphical Abstract
2. Scheme 1: Discovery of the LANCA three-component reaction. The reaction of pivalonitrile (1) with lithiated m...
  
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3. Scheme 2: Proposed mechanism of the LANCA three-component reaction to β-ketoenamides KE and pyridin-4-ol deri...
  
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4. Scheme 3: One-pot preparation of pyridin-4-ols PY and their subsequent transformations to highly substituted ...
  
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5. Scheme 4: Synthesis of β-ketoenamides KE by the LANCA three-component reaction of alkoxyallenes, nitriles and...
  
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6. Scheme 5: β-Ketoenamides KE36–43 derived from enantiopure components.
  
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7. Scheme 6: Bis-β-ketoenamides KE44–46 derived from aromatic dicarboxylic acids.
  
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8. Scheme 7: Conversion of alkyl propargyl ethers E into aryl-substituted β-ketoenamides KEAr and selected produ...
  
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9. Scheme 8: Condensation of LANCA-derived β-ketoenamides KE with ammonium salts to give 5-alkoxy-substituted py...
  
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10. Scheme 9: Synthesis of PM31–35 from β-ketoenamides KE37, KE38, KE40, KE41 and KE78 obtained by method A (NH₄O...
  
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11. Scheme 10: Synthesis of bis-pyrimidine derivatives PM36, PM39 and PM40 from β-ketoenamides KE44–46 by method A...
  
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12. Scheme 11: Functionalization of pyrimidine derivatives PM through selenium dioxide oxidations of PM5, PM9, PM15...
  
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13. Scheme 12: Conversion of 2-vinyl-substituted pyrimidine PM7 into aldehyde PM50; (NMO = N-methylmorpholine N-ox...
  
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14. Scheme 13: Deprotection of 5-alkoxy-substituted pyrimidines PM2, PM20 and PM29 and conversion into nonaflates ...
  
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15. Scheme 14: Palladium-catalyzed coupling reactions of PM54 and PM12 giving rise to new pyrimidine derivatives P...
  
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16. Scheme 15: Synthesis of pyrimidyl-substituted pyridyl nonaflate PM60.
  
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17. Scheme 16: Condensation of LANCA-derived β-ketoenamides KE with hydroxylamine hydrochloride leading to pyrimid...
  
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18. Scheme 17: Reactions of β-ketoenamides KE15 and KE7 with hydroxylamine hydrochloride leading to pyrimidine N-o...
  
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19. Scheme 18: Structures of pyrimidine N-oxides PO30–33 derived from β-ketoenamides KE43, KE45, KE78 and KE80.
  
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20. Scheme 19: Reduction of PO4 to PM5 and Boekelheide rearrangements of PO13, PO14, PO4 and PO30 to 4-acetoxymeth...
  
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21. Scheme 20: Deprotection of 4-acetoxymethyl-substituted pyrimidine derivatives PM61 and PM63, oxidations to for...
  
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22. Scheme 21: Synthesis of pyrimidinyl-substituted alkyne PM74 and conversion into furopyrimidine PM75 and Sonoga...
  
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23. Scheme 22: Trifluoroacetic acid-promoted conversion of LANCA-derived β-ketoenamides KE into oxazoles OX and 1,...
  
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24. Scheme 23: Conversion of β-ketoenamide KE79 into oxazole OX16 and transformation into 5-styryl-substituted oxa...
  
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25. Scheme 24: Mechanisms of the formation of 1,2-diketones DK and of acetyl-substituted oxazole derivatives OX.
  
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26. Scheme 25: Hydrogenolyses of benzyloxy-substituted β-ketoenamides KE52 and KE54 to 1,2-diketone DK14 and to di...
  
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27. Scheme 26: Conversions of 2,4-dicyclopropyl-substituted oxazole OX7 into oxazole derivatives OX18–20 (PPA = po...
  
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28. Scheme 27: Syntheses of vinyl and ethynyl-substituted oxazole derivatives OX21 and OX23 and their palladium-ca...
  
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29. Scheme 28: Synthesis of C₃-symmetric oxazole derivative OX28 and the STM current image of its 1-phenyloctane s...
  
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30. Scheme 29: Condensation of 1,2-diketones DK with o-phenylenediamine to quinoxalines QU1–7 (CAN = cerium ammoni...
  
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31. Scheme 30: The LANCA three-component reaction leading to β-ketoenamides KE and the structure of functionalized...
  
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Beilstein J. Org. Chem. 2019, 15, 655–678, doi:10.3762/bjoc.15.61

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Iodination of carbohydrate-derived 1,2-oxazines to enantiopure 5-iodo-3,6-dihydro-2H-1,2-oxazines and subsequent palladium-catalyzed cross-coupling reactions

Michal Medvecký,
Igor Linder,
Luise Schefzig,
Hans-Ulrich Reissig and
Reinhold Zimmer

Full Research Paper
Published 29 Dec 2016

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1. Graphical Abstract
2. Scheme 1: Access to enantiopure 3,6-dihydro-1,2-oxazines 3 via lithiated alkoxyallenes 1 and carbohydrate-der...
  
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3. Scheme 2: Iodination of 1,2-oxazines syn-3a–c and anti-3a,d leading to 5-iodo-substituted 1,2-oxazines syn-4a...
  
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4. Scheme 3: Sonogashira reactions of 4-methoxy-1,2-oxazines syn-4a, anti-4a and anti-4d leading to 5-alkynyl-su...
  
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5. Scheme 4: Sonogashira reactions of D-glyceraldehyde-derived 1,2-oxazines syn-4a–c leading to 5-alkynyl-substi...
  
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6. Scheme 5: Heck reactions of 1,2-oxazine syn-4a leading to 5-alkenyl-substituted 1,2-oxazines syn-13, syn-14 a...
  
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7. Scheme 6: Suzuki–Miyaura reactions of 1,2-oxazines syn-4a, syn-4b and anti-4d leading to 5-styryl-substituted...
  
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8. Scheme 7: Cross-coupling reaction of 1,2-oxazine anti-4d leading to 5-cyano-substituted 1,2-oxazine anti-25.
  
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9. Scheme 8: Desilylation of 1,2-oxazine syn-5 and subsequent click reaction with benzyl azide leading to 5-(1,2...
  
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10. Scheme 9: Hydrogenation of 1,2-oxazine syn-21 leading to γ-amino alcohols 27a,b and subsequent ring closure t...
  
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11. Scheme 10: Hydrogenation of 1,2-oxazine anti-24 to products anti-29 and anti-30.
  
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Beilstein J. Org. Chem. 2016, 12, 2898–2905, doi:10.3762/bjoc.12.289

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Stereoselective synthesis of tricyclic compounds by intramolecular palladium-catalyzed addition of aryl iodides to carbonyl groups

Jakub Saadi,
Christoph Bentz,
Kai Redies,
Dieter Lentz,
Reinhold Zimmer and
Hans-Ulrich Reissig

Full Research Paper
Published 16 Jun 2016

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1. Graphical Abstract
2. Scheme 1: Planned Heck reaction of A to compound B and serendipitous discovery of the palladium-catalyzed cyc...
  
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3. Scheme 2: Synthesis of compounds A (1–6) via methyl 2-siloxycyclopropanecarboxylates D, their alkylation to E...
  
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4. Scheme 3: Palladium-catalyzed reactions of methyl ketone 1 to tetralin derivative 7 and of isopropyl-substitu...
  
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5. Scheme 4: Palladium-catalyzed cyclization of diastereomeric cyclopentanone derivatives 3a/3b to products 11a ...
  
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6. Figure 1: Molecular structure (ORTEP, [14]) of compound 12a (thermal ellipsoids at 50% probability).
  
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7. Scheme 5: Palladium-catalyzed cyclizations of diastereomeric cyclohexanone derivatives 4a and 4b leading ster...
  
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8. Figure 2: Molecular structure (ORTEP, [14]) of compound 14a (thermal ellipsoids at 50% probability).
  
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9. Scheme 6: Palladium-catalyzed cyclizations of cycloheptanone derivatives 5a and 5b leading to products 15a an...
  
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10. Figure 3: Molecular structure (ORTEP, [14]) of compound 15a (thermal ellipsoids at 50% probability).
  
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11. Figure 4: Molecular structure (ORTEP [14]) of compound 15b (thermal ellipsoids at 50% probability).
  
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12. Scheme 7: Palladium-catalyzed cyclization of p-methoxy-substituted aryl iodide 6a/6b to compound 16.
  
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13. Scheme 8: Typical palladium-catalyzed cyclization of an o-iodoaniline derivative to a tricyclic tertiary alco...
  
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14. Scheme 9: Proposed transition state (TS) explaining the stereoselective formation of cyclization products.
  
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15. Scheme 10: Possible mechanism of the reduction of palladium(II) to palladium(0) by triethylamine (additional l...
  
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Beilstein J. Org. Chem. 2016, 12, 1236–1242, doi:10.3762/bjoc.12.118

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Synthesis of highly functionalized 2,2'-bipyridines by cyclocondensation of β-ketoenamides – scope and limitations

Paul Hommes and
Hans-Ulrich Reissig

Full Research Paper
Published 09 Jun 2016

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1. Graphical Abstract
2. Scheme 1: Synthesis of highly functionalized 2,2'-bipyridines 4a and 5b from symmetrical 1,3-diketones 1a and ...
  
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3. Scheme 2: Synthesis of β-ketoenamines 2c–e and of β-ketoenamides 3c–h.
  
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4. Scheme 3: Synthesis of α-methoxy-β-ketoenamine 2i, its N-acylation to 3i and the reaction of β-ketoenamide 3a...
  
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5. Scheme 4: Cyclizations of β-ketoenamide 3i leading to 2,2´-bipyridine derivative 4i or to the related 2-(2-py...
  
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6. Scheme 5: Suzuki-couplings of 2,2'-bipyrid-4-yl nonaflates 5a and 5b to compounds 9 and 10.
  
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7. Scheme 6: Palladium-catalyzed couplings of chloro-substituted 2,2'-bipyrid-4-yl nonaflate 5g leading to compo...
  
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Beilstein J. Org. Chem. 2016, 12, 1170–1177, doi:10.3762/bjoc.12.112

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Mechanical stability of bivalent transition metal complexes analyzed by single-molecule force spectroscopy

Manuel Gensler,
Christian Eidamshaus,
Maurice Taszarek,
Hans-Ulrich Reissig and
Jürgen P. Rabe

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Published 15 May 2015

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1. Graphical Abstract
2. Figure 1: Expected coordination complexes of monovalent and bivalent structures (1 and 2a–c, respectively) wi...
  
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3. Scheme 1: Synthesis of pyridine-PEG conjugate 5.
  
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4. Scheme 2: Synthesis of pyridine-PEG conjugate 10.
  
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5. Figure 2: Principle of the SMFS experiment. During retraction of the sample, possible interactions are probed...
  
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6. Figure 3: Potential energy diagrams according to the KBE model for simultaneous and successive bond rupture a...
  
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7. Figure 4: Most probable rupture forces plotted over their corresponding loading rate. Each point denotes for ...
  
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8. Figure 5: Possible rupture mechanism describing the extraordinary long rupture length of system 2c. Starting ...
  
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9. Figure 6: Most probable rupture forces at a logarithmic loading rate of 8.5 in relation to the corresponding ...
  
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Beilstein J. Org. Chem. 2015, 11, 817–827, doi:10.3762/bjoc.11.91

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Synthesis of multivalent carbohydrate mimetics with aminopolyol end groups and their evaluation as L-selectin inhibitors

Joana Salta,
Jens Dernedde and
Hans-Ulrich Reissig

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Published 05 May 2015

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1. Graphical Abstract
2. Scheme 1: General approach to divalent or trivalent carbohydrate mimetics on the basis of aminopyran 1 or ser...
  
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3. Scheme 2: Hydroxy group protection of aminopyran 1 to give compound 3, synthesis of amide 4 and subsequent de...
  
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4. Scheme 3: Attempt to synthesize protected divalent compound 6. Conditions: a) succinic acid dichloride, Et₃N,...
  
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5. Scheme 4: HATU-mediated synthesis of divalent amide 25 and trivalent amides 27 and 29. Conditions: a) HATU, Et...
  
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6. Scheme 5: Polysulfations of amides 5 and 13. Conditions: a) 1) SO₃∙DMF, DMF-d₇, 1 d, rt; 2) 1 M NaOH, 0 °C; 3...
  
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7. Scheme 6: Polysulfation of divalent amides 21 and 22 leading to tetrasulfated amides 32 and 33. Conditions: a...
  
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8. Scheme 7: Conversion of trivalent compound 27 into nonasulfated carbohydrate mimetic 34. Conditions: a) 1) SO₃...
  
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9. Figure 1: Structures of O-sulfated divalent amide 32 and trivalent amide 34 and their respective IC₅₀ values ...
  
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Beilstein J. Org. Chem. 2015, 11, 638–646, doi:10.3762/bjoc.11.72

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Synthesis of rigid p-terphenyl-linked carbohydrate mimetics

Maja Kandziora and
Hans-Ulrich Reissig

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Published 30 Jul 2014

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1. Graphical Abstract
2. Scheme 1: Approach to divalent carbohydrate mimetics 1 with rigid spacer and monovalent analogues 2.
  
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3. Scheme 2: Synthesis of (Z)-nitrone 6. Conditions: a) LiAlH₄, THF, 1 h, rt; b) 1. NaIO₄, CH₃CN/H₂O, 1 h, rt; 2...
  
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4. Scheme 3: [3 + 3]-Cyclization of (Z)-nitrone 6 with lithiated allene 9. Conditions: a) n-BuLi, THF, 15 min, −...
  
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5. Scheme 4: Synthesis of 1,2-oxazine 4 by acetal formation from 10. Conditions: a) 1-bromo-4-(dimethoxymethyl)b...
  
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6. Scheme 5: Synthesis of bicyclic ketone 11 by Lewis acid-induced rearrangement and reduction to alcohols 12a a...
  
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7. Scheme 6: Synthesis of bicyclic diols 15 and of trityl-protected bicyclic 1,2-oxazine 16. Conditions: a) SnCl₄...
  
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8. Scheme 7: Hydrogenolyses of bicyclic 1,2-oxazine derivatives 15a and 15b. Conditions: a) H₂, Pd/C, MeOH, EtOA...
  
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9. Scheme 8: Suzuki cross-coupling of 15a leading to biphenyl derivative 18 and hydrogenolysis to 19. Conditions...
  
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10. Scheme 9: Synthesis of N-benzylated p-terphenyl derivative 21 by Suzuki cross-coupling of 12a with 20 and sub...
  
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11. Scheme 10: Attempted reductive cleavage of the N–O bond of compound 21 by samarium diiodide and reaction of 12a...
  
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12. Scheme 11: Deprotection of compound 21 and samarium diiodide-mediated reaction of 26. Conditions: a) TBAF, THF...
  
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13. Scheme 12: Suzuki cross-coupling of compound 16. Conditions: Pd(PPh₃)₂Cl₂, 2 M Na₂CO₃, DMF, 80 °C, 3 d.
  
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14. Scheme 13: Hydrogenolysis of compound 27 and samarium diiodide-mediated reaction leading to compounds 30 and 31...
  
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Beilstein J. Org. Chem. 2014, 10, 1749–1758, doi:10.3762/bjoc.10.182

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The Flögel-three-component reaction with dicarboxylic acids – an approach to bis(β-alkoxy-β-ketoenamides) for the synthesis of complex pyridine and pyrimidine derivatives

Mrinal K. Bera,
Moisés Domínguez,
Paul Hommes and
Hans-Ulrich Reissig

Full Research Paper
Published 13 Feb 2014

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1. Graphical Abstract
2. Scheme 1: Flögel-three-component reaction of lithiated alkoxyallenes, nitriles and carboxylic acids providing...
  
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3. Scheme 2: Synthesis of bis(β-ketoenamides) 13–15 by three-component reactions of lithiated methoxyallene 8 wi...
  
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4. Scheme 3: Cyclocondensations of β-ketoenamides 13 and 14 to 4-hydroxypyridines 16, 18a and 18b, their subsequ...
  
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5. Scheme 4: Cyclocondensations of β-ketoenamides 13–15 with ammonium acetate to bis(pyrimidine) derivatives 23a...
  
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6. Scheme 5: Conversion of mono-pyrimidine derivative 24b into unsymmetrically substituted biphenylen-bridged py...
  
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7. Scheme 6: Condensation of β-ketoenamides 14 and 20 with hydroxylamine hydrochloride to pyridine-N-oxides 28 a...
  
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8. Scheme 7: Riley oxidation of bis(pyrimidine) derivative 23a and conversion of diol 32a into macrocycle 34.
  
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9. Figure 1: Optimized geometries of (a) E-configured and (b) Z-configured macrocycle 34 at B3LYP/6-31G(d,p) lev...
  
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10. Scheme 8: Dihydroxylation of the macrocyclic olefin 34 to diol 35 and subsequent esterification to the bis-(R...
  
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Beilstein J. Org. Chem. 2014, 10, 394–404, doi:10.3762/bjoc.10.37

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Synthesis of new enantiopure poly(hydroxy)aminooxepanes as building blocks for multivalent carbohydrate mimetics

Léa Bouché,
Maja Kandziora and
Hans-Ulrich Reissig

Full Research Paper
Published 20 Jan 2014

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1. Graphical Abstract
2. Scheme 1: General approach to enantiopure the poly(hydroxy)aminopyrans D (n = 0) and the aminooxepanes D (n =...
  
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3. Scheme 2: Synthesis of (Z)-nitrone 3. Conditions: a) 1. p-Bromobenzaldehyde dimethylacetal, TFA, DMF, rt, 5 d...
  
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4. Scheme 3: Synthesis of 1,2-oxazines syn-7, syn-9 and syn-10. Conditions: a) n-BuLi, THF, −40 °C, 15 min; b) 1...
  
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5. Figure 1: Proposed transition structure for the addition of lithiated TMSE-allene 5 to chiral nitrones 3, 6 a...
  
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6. Scheme 4: Synthesis of ketones 11, 12 and 13 with a bicyclic 1,2-oxazine skeleton by Lewis acid-induced rearr...
  
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7. Scheme 5: Proposed extended chair-like conformation with Zimmerman–Traxler-type transition state.
  
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8. Figure 2: GOESY–NMR spectrum (CDCl₃, 500 MHz) of bicyclic 1,2-oxazine 13: irradiation of the 2-H proton. [GOE...
  
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9. Scheme 6: Synthesis of triols 14, 15 and 16 by reduction of the carbonyl group and deprotection. Conditions: ...
  
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10. Scheme 7: Synthesis of propargylic ether 18. Conditions: a) propargyl bromide, NaOH, TBAI, H₂O/CH₂Cl₂, −20 °C...
  
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11. Scheme 8: Synthesis of tricyclic compound 20, bicyclic azide 24 and bicyclic amine 25. Conditions: a) MsCl, Et...
  
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12. Scheme 9: Hydrogenolyses of bicyclic and tricyclic 1,2-oxazines 14, 15 and 20 to aminooxepanes 26, 27 and 28....
  
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13. Figure 3: Proposed structures of the observed side products 29 and 30 during the hydrogenolyses of 14 and 15.
  
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14. Scheme 10: Hydrogenolyses of bicyclic 1,2-oxazines to aminooxepanes 26, 31 and 32 and to diaminooxepane 33 und...
  
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Beilstein J. Org. Chem. 2014, 10, 213–223, doi:10.3762/bjoc.10.17

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Stereodivergent synthesis of jaspine B and its isomers using a carbohydrate-derived alkoxyallene as C₃-building block

Volker M. Schmiedel,
Stefano Stefani and
Hans-Ulrich Reissig

Full Research Paper
Published 19 Nov 2013

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1. Graphical Abstract
2. Scheme 1: Structure of jaspine B 1 and its stereoisomers 2–4.
  
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3. Scheme 2: Retrosynthetic analysis of jaspine B leading to pentadecanal and an alkoxyallene.
  
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4. Scheme 3: Synthesis of racemic dihydrofuran 8.
  
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5. Scheme 4: Synthesis of racemic jaspine B rac-1 and its diastereomer rac-2.
  
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6. Scheme 5: Synthesis of dihydrofurans 14 and 15.
  
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7. Scheme 6: Synthesis of jaspine B (1) and its (2S,3R,4R)-diastereomer 2.
  
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8. Scheme 7: Protection and separation of the diastereomers.
  
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9. Scheme 8: Reduction of the separated diastereomers leading to jaspine B (1) and its diastereomer 2.
  
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10. Scheme 9: Route to ent-jaspine B (3) and the (2R,3S,4S)-diastereomer 4.
  
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Beilstein J. Org. Chem. 2013, 9, 2564–2569, doi:10.3762/bjoc.9.291

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Carbohydrate-auxiliary assisted preparation of enantiopure 1,2-oxazine derivatives and aminopolyols

Marcin Jasiński,
Dieter Lentz and
Hans-Ulrich Reissig

Full Research Paper
Published 30 Apr 2012

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1. Graphical Abstract
2. Scheme 1: Reactivity of N-glycosyl nitrones 1 towards dipolarophiles and nucleophiles leading to products of ...
  
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3. Scheme 2: Additions of lithiated alkoxyallenes to L-erythrose-derived nitrone 1a leading to 3,6-dihydro-2H-1,...
  
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4. Figure 1: By-products 4 and 5 isolated from the reaction of nitrone 1a with lithiated methoxyallene.
  
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5. Figure 2: Single-crystal X-ray analysis of (3R)-3a (ellipsoids are drawn at a 50% probability level).
  
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6. Figure 3: Model proposed for the addition of lithiated allenes to nitrone 1a.
  
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7. Scheme 3: Speculative mechanistic suggestion for the formation of tetrasubstituted pyrrole derivative 5.
  
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8. Scheme 4: Introduction of a 5-hydroxy group into 1,2-oxazine derivatives 3 by a hydroboration/oxidation proto...
  
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9. Scheme 5: Samarium diiodide-induced ring opening of tetrahydro-2H-1,2-oxazine derivatives 12 and 13.
  
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10. Scheme 6: Reaction of tetrahydro-2H-1,2-oxazine 18 with samarium diiodide. (a) NaH (1.4 equiv), BnBr (1.2 equ...
  
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11. Scheme 7: Attempted synthesis of pyrrolidine derivatives from precursor 13. (a) TMSCl (1.5 equiv), imidazole,...
  
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12. Scheme 8: Synthesis of TBS-protected tetrahydro-2H-1,2-oxazine 27 and its transformation into pyrrolidine der...
  
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Beilstein J. Org. Chem. 2012, 8, 662–674, doi:10.3762/bjoc.8.74

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A practical two-step procedure for the preparation of enantiopure pyridines: Multicomponent reactions of alkoxyallenes, nitriles and carboxylic acids followed by a cyclocondensation reaction

Christian Eidamshaus,
Roopender Kumar,
Mrinal K. Bera and
Hans-Ulrich Reissig

Full Research Paper
Published 13 Jul 2011

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1. Graphical Abstract
2. Scheme 1: Preparation of β-ketoenamides and subsequent cyclocondensation to 4-hydroxypyridines. a) Et₂O, −40 ...
  
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3. Scheme 2: Mechanistic rational for the formation of β-ketoenamides 16.
  
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4. Scheme 3: Reaction of proline derivative 45 and formation of β-ketoenamide 47 and enolester 48.
  
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5. Figure 1: ¹H NMR spectra of 49 and the mixture of diastereoisomers 49 and 49’.
  
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6. Scheme 4: Synthesis of pyrid-4-yl nonaflate 52.
  
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7. Scheme 5: O-Methylation of pyridine derivatives 22 and 30 followed by desilylation.
  
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8. Scheme 6: Formation of 5-alkoxypyrimidines from β-alkoxy-β-ketoenamides.
  
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Beilstein J. Org. Chem. 2011, 7, 962–975, doi:10.3762/bjoc.7.108

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Highly substituted benzannulated cyclooctanol derivatives by samarium diiodide-induced cyclizations

Jakub Saadi,
Irene Brüdgam and
Hans-Ulrich Reissig

Full Research Paper
Published 28 Dec 2010

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1. Graphical Abstract
2. Scheme 1: SmI₂-induced cyclizations of styryl-substituted γ-ketoesters A to benzannulated cyclooctanol deriva...
  
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3. Scheme 2: Three-step synthesis of precursor 4 starting from siloxycyclopropane derivative 1.
  
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4. Scheme 3: Attempted cyclizations of diastereomeric cycloheptanone derivatives 5a and 5b.
  
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5. Scheme 4: Samarium diiodide-induced cyclization of γ-ketoester 7a to tricyclic compound 8.
  
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6. Scheme 5: Samarium diiodide-induced cyclizations of methyl ketone 4 and iso-propyl ketone 11.
  
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7. Figure 1: NOESY-correlation for compound 10.
  
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8. Figure 2: NOESY-correlation for compound 9.
  
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9. Scheme 6: Assumed transition structures and intermediates A, B, or C for the cyclizations of (2-propenyl)phen...
  
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10. Scheme 7: Reductive fragmentation of highly hindered ketoester 14.
  
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11. Scheme 8: Samarium diiodide-induced cyclization of phenyl-substituted substrate 16 leading to lactones 17a an...
  
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12. Figure 3: Molecular structure (Diamond [52]) of compound 17b.
  
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13. Scheme 9: Samarium diiodide-induced cyclizations of (E)-(1-propenyl)phenyl-substituted γ-ketoesters 18, 21, a...
  
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14. Figure 4: Proposed transition structure for the cyclization of (E)-1-propenyl-substituted substrates (HMPA li...
  
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15. Scheme 10: Attempted samarium diiodide-induced cyclizations with (E)-1-propenyl-substituted precursors 26a and ...
  
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16. Scheme 11: Attempted samarium diiodide-induced cyclization of (Z)-1-propenyl-substituted precursor 30.
  
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17. Scheme 12: Samarium diiodide-induced cyclizations of γ-ketoesters 33 and 36.
  
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18. Scheme 13: Samarium diiodide-induced cyclizations of diastereomeric stilbenyl-substituted γ-ketoesters 38a and ...
  
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19. Figure 5: Molecular structure (Diamond [52]) of compound 40.
  
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20. Scheme 14: Attempted cyclization of β-dialkyl-substituted styrene derivative 41.
  
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21. Scheme 15: Typical products of samarium diiodide-induced 8-endo-trig cyclizations of α-styryl-substituted γ-ke...
  
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22. Scheme 16: Typical products of samarium diiodide-induced 8-endo-trig cyclizations of β-styryl-substituted γ-ke...
  
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Supp. Info

Beilstein J. Org. Chem. 2010, 6, 1229–1245, doi:10.3762/bjoc.6.141

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Addition of lithiated enol ethers to nitrones and subsequent Lewis acid induced cyclizations to enantiopure 3,6-dihydro-2H-pyrans – an approach to carbohydrate mimetics

Fabian Pfrengle and
Hans-Ulrich Reissig

Full Research Paper
Published 09 Jul 2010

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1. Graphical Abstract
2. Scheme 1: Synthesis of 3,6-dihydro-2H-pyrans D.
  
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3. Scheme 2: Addition of lithiated enol ether 1a to nitrone 2c/Et₂AlCl.
  
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4. Scheme 3: Mechanistic proposal for the transformation of syn-4a into cis-5a in the presence of TMSOTf.
  
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5. Scheme 4: Unsuccessful attempt to cyclize hydroxylamine derivative syn-4f.
  
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6. Scheme 5: Functionalizations of the enol ether moiety of cis-5a leading to compounds 8–11.
  
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7. Scheme 6: Transformations of the enol ether moiety of trans-5a leading to products 13–15.
  
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8. Scheme 7: Bromination of bicyclic dihydropyran trans-5b affording 16.
  
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9. Scheme 8: Synthesis of epoxypyran 18 by bromination of cis-5d.
  
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10. Scheme 9: Oxidative cleavage of dihydropyran 19 to lactone 20.
  
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11. Scheme 10: Transformation of α-bromoketone 15 into nitrone 21 by an internal redox reaction.
  
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12. Scheme 11: Transformation of α-bromoketone 11 into nitrone 21.
  
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13. Scheme 12: Synthesis of diastereomeric aminopyrans 24 and 26.
  
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14. Scheme 13: Synthesis of diastereomeric aminopyrans 28 and 30.
  
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15. Scheme 14: Synthesis of triamides 31 and 32.
  
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Beilstein J. Org. Chem. 2010, 6, No. 75, doi:10.3762/bjoc.6.75

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Preparation of pyridine-3,4-diols, their crystal packing and their use as precursors for palladium-catalyzed cross-coupling reactions

Tilman Lechel,
Irene Brüdgam and
Hans-Ulrich Reissig

Full Research Paper
Published 29 Apr 2010

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1. Graphical Abstract
2. Scheme 1: Deprotection of 3-alkoxypyridinols 1 to pyridine-3,4-diols 2. ^aMethod a: Pd/C, H₂, MeOH, rt, 1 d; ^b...
  
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3. Figure 1: X-ray crystal structure of compound 2c/2c′.
  
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4. Scheme 2: Conversion of pyridine-3,4-diols 2 into pyridinediyl bistriflates or -nonaflates 3. a) Et₃N, Rf₂O, ...
  
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5. Scheme 3: Sonogashira couplings of pyridinediyl bis(perfluoroalkanesulfonates) 3. a) Pd(PPh₃)₄ [or Pd(OAc)₂/P...
  
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6. Figure 2: Absorption and fluorescence spectra of compounds 4b and 4c.
  
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Supp. Info

Beilstein J. Org. Chem. 2010, 6, No. 42, doi:10.3762/bjoc.6.42

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Palladium- catalyzed cross coupling reactions of 4-bromo- 6H-1,2-oxazines

Reinhold Zimmer,
Elmar Schmidt,
Michal Andrä,
Marcel-Antoine Duhs,
Igor Linder and
Hans-Ulrich Reissig

Preliminary Communication
Published 16 Sep 2009

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Album
1. Graphical Abstract
2. Scheme 1: Brominations of 6H-1,2-oxazines. a) Br₂, Et₂O, −30 °C, 2 h. b) Et₃N, −30 °C to r.t., overnight.
  
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3. Scheme 2: Chlorinations of 6H-1,2-oxazines. a) Cl₂, Et₂O, −30 °C. b) Et₃N, −30 °C to r.t.
  
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4. Scheme 3: Suzuki-couplings of 4-bromo-6H-1,2-oxazines. a) ArB(OH)₂, Pd(PPh₃)₄, Na₂CO₃, toluene, 80 °C, 3 h.
  
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5. Scheme 4: Sonogashira-couplings of 4-bromo-6H-1,2-oxazines. a) PdCl₂(PPh₃)₂, CuI, Et₃N, toluene, r.t., 6–20 h....
  
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6. Scheme 5: Sonogashira-couplings of 4,5-dibromo-6H-1,2-oxazines. a) PdCl₂(PPh₃)₂, CuI, Et₃N, toluene, r.t., 4 ...
  
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7. Scheme 6: Preparation of trisubstituted pyridine derivatives: a) BF₃·OEt₂, CH₂Cl₂, −78 °C to r.t., overnight.
  
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Beilstein J. Org. Chem. 2009, 5, No. 44, doi:10.3762/bjoc.5.44

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