Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

Total synthesis of leopolic acid A, a natural 2,3-pyrrolidinedione with antimicrobial activity

• Atul A. Dhavan,
• Rahul D. Kaduskar,
• Loana Musso,
• Leonardo Scaglioni,
• Piera Anna Martino and
• Sabrina Dallavalle

Beilstein J. Org. Chem. 2016, 12, 1624–1628, doi:10.3762/bjoc.12.159

• ester-activated N-Boc-valine to obtain compound 8 (Scheme 1). Treatment with DIBAL-H led to the reduction of both the ester and the CO group of the valine moiety (9). Compound 9 was obtained as a 9:1 mixture of diastereomers, the syn (S,S) diastereomer being the major one. The selectivity of the

Selective bromochlorination of a homoallylic alcohol for the total synthesis of (−)-anverene

• Frederick J. Seidl and
• Noah Z. Burns

Beilstein J. Org. Chem. 2016, 12, 1361–1365, doi:10.3762/bjoc.12.129

• recrystallization, over 100 mg of 1 was isolated as a single diastereomer and constitutional isomer, culminating a 9-step route with an overall yield of 21.8%. Conclusion In conclusion, a new protocol for the catalytic enantioselective bromochlorination reaction has been developed which has enabled the highly

Synergistic chiral iminium and palladium catalysis: Highly regio- and enantioselective [3 + 2] annulation reaction of 2-vinylcyclopropanes with enals

• Haipan Zhu,
• Peile Du,
• Jianjun Li,
• Ziyang Liao,
• Guohua Liu,
• Hao Li and
• Wei Wang

Beilstein J. Org. Chem. 2016, 12, 1340–1347, doi:10.3762/bjoc.12.127

• due to the minimization of the A[1][3] interaction. Therefore, it is observed 3a’ produced from corresponding 8a’ as the major diastereomer whereas 3a” as minor one. Conclusion We have developed a cooperative catalytic strategy for highly regio- and enantioselective [3 + 2] cycloaddition reactions of

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

Beilstein J. Org. Chem. 2016, 12, 1236–1242, doi:10.3762/bjoc.12.118

• ketones 3–6 that led to tricyclic compounds. Methyl ketone 1 provided under the reaction conditions (2 mol % Pd(PPh3)4, 3.5 equivalents NEt3, DMF, 110 °C, 3 d) that had been optimized with compound 4 a moderate yield of the tetralin derivative 7 formed as a single diastereomer (Scheme 3). Although the

Conjugate addition–enantioselective protonation reactions

• James P. Phelan and
• Jonathan A. Ellman

Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116

• er) (Scheme 23b) [46]. This enantioselective addition process could be applied to a racemic mixture of axially chiral N-(2-tert-butylphenyl)itaconimide (98), furnishing atropisomers 99a and 99b as a stable and separable 1:1 mixture. A higher enantioselectivity was observed for the anti-diastereomer

Unusual traits of cis and trans-2,3-dibromo-1,1-dimethylindane on the way from 1,1-dimethylindene to 2-bromo-, 3-bromo-, and 2,3-dibromo-1,1-dimethylindene

• Rudolf Knorr,
• David S. Stephenson,
• Ernst Lattke,
• Petra Böhrer and
• Jakob Ruhdorfer

Beilstein J. Org. Chem. 2016, 12, 1178–1184, doi:10.3762/bjoc.12.113

• -dibromo-1,1-dimethylindanes violate the rule by means of their values of 3J(cis) = 6.1 Hz and 3J(trans) = 8.4 Hz. The stereoselective formation of the trans diastereomer from 1,1-dimethylindene was improved with the tribromide anion (Br3−) as the brominating agent in place of elemental bromine; the

• established [1][2][3]. With indene as a cyclic olefin, the major product trans-1,2-dibromoindane was formed through antarafacial addition; the accompanying cis diastereomer resulted through the suprafacial bromine addition and rarely [4] exceeded 30% of the diastereomeric trans/cis product mixture. For the

• Hz, whereas the trans diastereomer exhibited 3J(1-H,2-H) = 1.3 Hz [6]. However, we report here on the closely related trans diastereomer of 2,3-dibromo-1,1-dimethylindane (trans-1) whose grossly deviating value of 3J(2-H,3-H) = 8.4 Hz violates the above 3JH,H rule. Results and Discussion The addition

Chiral cyclopentadienylruthenium sulfoxide catalysts for asymmetric redox bicycloisomerization

• Barry M. Trost,
• Michael C. Ryan and
• Meera Rao

Beilstein J. Org. Chem. 2016, 12, 1136–1152, doi:10.3762/bjoc.12.110

• functionality on the substrate in question. For example, Hayashi has shown that a rhodium/phosphoramidite catalysis is particularly effective for asymmetric [5 + 2] cycloaddition reactions (Scheme 2b). The (S,R,R)-diastereomer of the Feringa-style phosphoramidite ligand proved to be crucial to both the yield

• and enantioselectivity of this reaction, as there was a severe matched/mismatched effect observed with another diastereomer. In contrast to the ruthenium-catalyzed [5 + 2] cycloaddition of enynes, which is thought to proceed through a ruthenacyclopentene intermediate [26], it has been proposed that

• sulfinamides [48]. The application of this method to the synthesis of our chiral sulfoxide tethers is presented in Scheme 4. Tosyl protection of the primary amine of (+)-norephedrine and treatment with thionyl chloride furnishes chiral oxathiazolidine 2-oxide 7 as a single diastereomer in 87% yield over two

Modular synthesis of the pyrimidine core of the manzacidins by divergent Tsuji–Trost coupling

• Sebastian Bretzke,
• Stephan Scheeff,
• Felicitas Vollmeyer,
• Friederike Eberhagen,
• Frank Rominger and
• Dirk Menche

Beilstein J. Org. Chem. 2016, 12, 1111–1121, doi:10.3762/bjoc.12.107

• required for manzacidin A. Possibly, the higher selectivity observed for the conversion of 29 as compared to 30 may be due to initial problems during the work-up. Finally, the addition could be effected giving the desired diastereomer 31 in high yields (72%) and the minor isomer 32 that was likewise

• obtained (24%) could be readily removed by column chromatography. The configuration of 31 was initially assigned by Mosher ester analysis of the free amine 36 (Scheme 6) and finally proven in an indirect manner by an X-ray crystallography of the minor diastereomer 32. Within the course of this study also

• acetate and finally purified by column chromatography on silica gel (120 g) with ethyl acetate/hexane 1:9 as eluent, which yielded the desired diasteromers 31 (major diastereomer) and 32 (minor diastereomer) as light yellow oils (96 %, dr = 1:3). Major diastereomer SSR (1.13 g, 3.39 mmol, 72%): Rf 0.1

Towards the total synthesis of keramaphidin B

• Pavol Jakubec,
• Alistair J. M. Farley and
• Darren J. Dixon

Beilstein J. Org. Chem. 2016, 12, 1096–1100, doi:10.3762/bjoc.12.104

• reported cinchonine-derived bifunctional thiourea catalyst 12 afforded the addition product 13 in high yield with good levels of diastereo- and enantioselectivity (95:5 dr, 90:10 er for the major diastereomer 13). The relative stereochemical configuration of the minor diastereomeric product 14 was

• determined by single X-ray crystallographic analysis of rac-14 (see Supporting Information File 1) and revealed that the major diastereomer 13 indeed possessed the necessary stereochemical configuration [21] for accessing keramaphidin B, assuming the chemoselectivity of the nitro-Mannich lactamisation

• the model system, identical levels of diastereo- and enantiocontrol were observed in the formation of 7 (92% yield). Treatment of the major diastereomeric product 7 with hept-5-yn-1-amine (16) and formaldehyde in boiling methanol afforded the lactam 6 in 56% yield as a single diastereomer in 91:9 er

The synthesis of functionalized bridged polycycles via C–H bond insertion

• Jiun-Le Shih,
• Po-An Chen and
• Jeremy A. May

Beilstein J. Org. Chem. 2016, 12, 985–999, doi:10.3762/bjoc.12.97

• catalyst (Scheme 27) [102][103]. Again, the formation of a 1,3-dipole (see 127) allows for a cycloaddition, though this example is intermolecular in nature. One of the ethereal ethyl groups in 128 is consequently poised for C–H bond insertion by the tungsten carbene to give 129 as a single diastereomer

1H-Imidazol-4(5H)-ones and thiazol-4(5H)-ones as emerging pronucleophiles in asymmetric catalysis

• Antonia Mielgo and
• Claudio Palomo

Beilstein J. Org. Chem. 2016, 12, 918–936, doi:10.3762/bjoc.12.90

• (Scheme 2, compounds 13–15) proceeded with poor diastereocontrol but the results were improved by changing to catalyst C2 [62]. Nonetheless, in both cases the enantioselectivity for the major diastereomer was excellent. Finally, and starting from the corresponding bicyclic imidazolones, quaternary proline

Scope and mechanism of the highly stereoselective metal-mediated domino aldol reactions of enolates with aldehydes

• M. Emin Cinar,
• Bernward Engelen,
• Martin Panthöfer,
• Hans-Jörg Deiseroth,
• Jens Schlirf and
• Michael Schmittel

Beilstein J. Org. Chem. 2016, 12, 813–824, doi:10.3762/bjoc.12.80

• gallium at 0 °C and Sn(IV) at 25 °C a diastereomer of 5a also formed in 20 and 29% yields, respectively. Generally, with nearly all metals, the yield of 5a increased dramatically when the temperature was raised to 25 °C, but dropped at higher temperatures. The decreased yield at 67 °C may emerge from the

• ligands may simply act as "innocent bystander ligands" in the reaction cascade. Since we have been able to obtain 5a with GaCl3 in a diastereomerically pure form at 25 °C – although at low temperature a sizeable amount of 20% of a second diastereomer was formed – it is reasonable to assume a reversible

Muraymycin nucleoside-peptide antibiotics: uridine-derived natural products as lead structures for the development of novel antibacterial agents

• Daniel Wiegmann,
• Stefan Koppermann,
• Marius Wirth,
• Giuliana Niro,
• Kristin Leyerer and
• Christian Ducho

Beilstein J. Org. Chem. 2016, 12, 769–795, doi:10.3762/bjoc.12.77

• unwanted diastereomer 22, the synthesis was finished with the desired minor component 23. Boc deprotection followed by reaction with guanidinylation reagent 24 gave bicyclic compound 25. The next steps included a desulfonylation and the reaction with 26 leading to protected epicapreomycidine-containing

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• , when a different derivative of L-diphenylprolinol is used, a different diastereomer of the product is obtained. When along with N-Boc-substituted oxindole 218, substituted derived nitro-alkene 82 and substituted unsaturated aldehyde 154, a bifunctional quinine-derived thiourea 57 and L-diphenylprolinol

• with another derivative of 220, organocatalyst 214, another diastereomer was obtained of the desired product 221 (Scheme 69). This domino Michael–Michael aldol reaction provides the product in an excellent 92% yield, excellent enantiomeric excess (>99%) and good diastereoselectivity (9:2.5:1). Dixon

• McGarrigle, Galan and co-workers (Scheme 77) [96]. In this reaction the reagent is 2,3,4-trisubstituted dihydro-pyran 247 and the product is the corresponding α-galactopyranose 248. This reaction provides exclusively the α-diastereomer in a yield up to 98%. In 2013, Schmidt and co-workers described the use

Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

• Rajeev S. Menon,
• Akkattu T. Biju and
• Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

• Michael adducts into the benzoin product. The prolinol catalyst 60, on the other hand, mediates the epimerisation of the less reactive diastereomer. This synergy leads to the enrichment of the diastereomeric ratio of the final product 64 (Scheme 38) [55]. Enders developed a closely related iminium-cross

Simple activation by acid of latent Ru-NHC-based metathesis initiators bearing 8-quinolinolate co-ligands

• Julia Wappel,
• Roland C. Fischer,
• Luigi Cavallo,
• Christian Slugovc and
• Albert Poater

Beilstein J. Org. Chem. 2016, 12, 154–165, doi:10.3762/bjoc.12.17

• ). The minor isomer 2a (28% yield) was identified as the OC-6-14 diastereomer featuring the two oxygen atoms in trans disposition (and the nitrogen atom trans to the benzylidene ligand). The major isomer 2b (57% yield) is the OC-6-32 diastereomer bearing the two oxygen ligands in cis disposition (and one

Diastereoselective Ugi reaction of chiral 1,3-aminoalcohols derived from an organocatalytic Mannich reaction

• Samantha Caputo,
• Andrea Basso,
• Lisa Moni,
• Renata Riva,
• Valeria Rocca and
• Luca Banfi

Beilstein J. Org. Chem. 2016, 12, 139–143, doi:10.3762/bjoc.12.15

• and NMR analogies suggest that the main diastereomer was always the same, with one notable exception: product 6f obtained in the absence of Lewis acid. In this case, it was necessary to carry out the reaction in THF/iPrOH because the isocyanide was poorly soluble in MeOH, and thus the unexpected

Catalytic asymmetric formal synthesis of beraprost

• Yusuke Kobayashi,
• Ryuta Kuramoto and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2015, 11, 2654–2660, doi:10.3762/bjoc.11.285

• . Therefore, the product was isolated as alcohol 15 after a one-pot reduction of the ketone moiety (60% in four steps from 6), along with the minor diastereomer at C1 position (dr > 18:1). These results mean that the stereochemistry at the C2 position was fully controlled, presumably due to hydride attack

Synthesis of Xenia diterpenoids and related metabolites isolated from marine organisms

• Tatjana Huber,
• Lara Weisheit and
• Thomas Magauer

Beilstein J. Org. Chem. 2015, 11, 2521–2539, doi:10.3762/bjoc.11.273

• acetylide to the carbonyl group of 69, followed by desilylation under basic conditions gave rise to (±)-ethynylcarbinol, which was separated by chiral HPLC. The desired diastereomer was then transformed to benzene sulfinate ester 70. A palladium-catalyzed [2,3]-sigmatropic rearrangement formed an isomeric

• synthesized in four steps. Esterification with (R)-(+)-citronellic acid (127) yielded a single diastereomer of ester 128. Addition of lithium diisopropylamide to a mixture of 128, trimethylsilyl chloride and triethylamine initiated an Ireland–Claisen rearrangement [63] which gave carboxylic acid 129 in 85

Bromotyrosine-derived alkaloids from the Caribbean sponge Aplysina lacunosa

• Qun Göthel,
• Thanchanok Sirirak and
• Matthias Köck

Beilstein J. Org. Chem. 2015, 11, 2334–2342, doi:10.3762/bjoc.11.254

• proposed to be the same as of 19, chemical fragmentation of 5 releasing from the sponge Aplysina spp. after induction by tissue damage (Figure 4). However, the conversion from 5 to 19 has not been confirmed. A single data set in the 13C NMR spectrum supported the presence of one diastereomer of 1. Compound

• diastereomer of 2 was confirmed by a single data set in the 13C NMR spectrum. Compound 3 was isolated together with N-methylaerophobin-2 (15) as a mixture (approximate ratio 1:5). The ESIMS spectrum exhibited a 1:2:1 ion cluster at m/z 457/459/461, indicating the presence of two bromine atoms. The HRMS–ESI

Synthesis of D-fructose-derived spirocyclic 2-substituted-2-oxazoline ribosides

• Madhuri Vangala and
• Ganesh P. Shinde

Beilstein J. Org. Chem. 2015, 11, 2289–2296, doi:10.3762/bjoc.11.249

• spiro 2-substituted-2-oxazolines were stable and obtained as a single diastereomer. To assign the relative stereochemistry at the anomeric center, compounds 11a and 17a were subjected to 2D NMR analysis. In the NOESY spectra of compounds 11a and 17a, the cross peaks between C1–H, C1–H’ and CH3 groups of

• as a single diastereomer in good yield. In the absence of the nucleophile, the oxacarbenium-ion intermediate of protected D-psicofuranose derivatives underwent spiroketalization to give di-D-fructose dianhydrides. Given the established, pharmacological applications of riboside derivatives, these

Investigation of the role of stereoelectronic effects in the conformation of piperidones by NMR spectroscopy and X-ray diffraction

• Cesar Garcias-Morales,
• David Ortegón-Reyna and
• Armando Ariza-Castolo

Beilstein J. Org. Chem. 2015, 11, 1973–1984, doi:10.3762/bjoc.11.213

• , only the diastereomer with the phenyl groups in the cis orientation was obtained. This is because in the transition state (TS) for the cis compounds the energy of the 1H,3H-allylic strain (A1,3) is lower in comparison with the TS trans,1Ar,3H-allylic strain [57], which is caused by the hindrance effect

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• compound 269 was obtained from oxabicyclo adduct 268 by a domino metathesis sequence in the presence of catalyst 2. Moreover, compound 269 was obtained as a single diastereomer and constitutes the core structure of phelligridin G (Scheme 55). In 2009, Hanson’s group reported [56] the synthesis of

Synthesis of novel N-cyclopentenyl-lactams using the Aubé reaction

• Madhuri V. Shinde,
• Rohini S. Ople,
• Ekta Sangtani,
• Rajesh Gonnade and
• D. Srinivasa Reddy

Beilstein J. Org. Chem. 2015, 11, 1060–1067, doi:10.3762/bjoc.11.119

• the desired azido alcohol (±)-3 as an 8:1 regioisomeric mixture. However, we could neither purify nor isolate compound (±)-3 in pure form, which was always accompanied by an undesired isomeric compound. To confirm whether it is a diastereomer or regioisomer, we performed two derivatization reactions

• literature and the data were compared with that reported [34]. The structure of the minor diastereomer (±)-4’ was assigned based on 2D NMR correlations. Secondly, the azido alcohol (±)-3 was subjected to a click reaction with phenylacetylene under standard conditions and the resulting two compounds, (±)-5

• and our initial designs. ORTEP plot of triol (±)-12. The Aubé reaction and its selected applications. Top: synthesis of azido alcohol derivative 3 and bottom: structural elucidation of the minor diastereomer. Aubé reaction of cylopentenyl azido alcohol 3 with cyclohexanone. Substrate scope of the