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2 article(s) from Kumar, Roopender

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

Beilstein J. Org. Chem. 2019, 15, 655–678, doi:10.3762/bjoc.15.61

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Graphical Abstract

Scheme 1: Discovery of the LANCA three-component reaction. The reaction of pivalonitrile (1) with lithiated m...

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Scheme 2: Proposed mechanism of the LANCA three-component reaction to β-ketoenamides KE and pyridin-4-ol deri...

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Scheme 3: One-pot preparation of pyridin-4-ols PY and their subsequent transformations to highly substituted ...

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Scheme 4: Synthesis of β-ketoenamides KE by the LANCA three-component reaction of alkoxyallenes, nitriles and...

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Scheme 5: β-Ketoenamides KE36–43 derived from enantiopure components.

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Scheme 6: Bis-β-ketoenamides KE44–46 derived from aromatic dicarboxylic acids.

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Scheme 7: Conversion of alkyl propargyl ethers E into aryl-substituted β-ketoenamides KEAr and selected produ...

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Scheme 8: Condensation of LANCA-derived β-ketoenamides KE with ammonium salts to give 5-alkoxy-substituted py...

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Scheme 9: Synthesis of PM31–35 from β-ketoenamides KE37, KE38, KE40, KE41 and KE78 obtained by method A (NH₄O...

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Scheme 10: Synthesis of bis-pyrimidine derivatives PM36, PM39 and PM40 from β-ketoenamides KE44–46 by method A...

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Scheme 11: Functionalization of pyrimidine derivatives PM through selenium dioxide oxidations of PM5, PM9, PM15...

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Scheme 12: Conversion of 2-vinyl-substituted pyrimidine PM7 into aldehyde PM50; (NMO = N-methylmorpholine N-ox...

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Scheme 13: Deprotection of 5-alkoxy-substituted pyrimidines PM2, PM20 and PM29 and conversion into nonaflates ...

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Scheme 14: Palladium-catalyzed coupling reactions of PM54 and PM12 giving rise to new pyrimidine derivatives P...

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Scheme 15: Synthesis of pyrimidyl-substituted pyridyl nonaflate PM60.

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Scheme 16: Condensation of LANCA-derived β-ketoenamides KE with hydroxylamine hydrochloride leading to pyrimid...

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Scheme 17: Reactions of β-ketoenamides KE15 and KE7 with hydroxylamine hydrochloride leading to pyrimidine N-o...

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Scheme 18: Structures of pyrimidine N-oxides PO30–33 derived from β-ketoenamides KE43, KE45, KE78 and KE80.

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Scheme 19: Reduction of PO4 to PM5 and Boekelheide rearrangements of PO13, PO14, PO4 and PO30 to 4-acetoxymeth...

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Scheme 20: Deprotection of 4-acetoxymethyl-substituted pyrimidine derivatives PM61 and PM63, oxidations to for...

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Scheme 21: Synthesis of pyrimidinyl-substituted alkyne PM74 and conversion into furopyrimidine PM75 and Sonoga...

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Scheme 22: Trifluoroacetic acid-promoted conversion of LANCA-derived β-ketoenamides KE into oxazoles OX and 1,...

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Scheme 23: Conversion of β-ketoenamide KE79 into oxazole OX16 and transformation into 5-styryl-substituted oxa...

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Scheme 24: Mechanisms of the formation of 1,2-diketones DK and of acetyl-substituted oxazole derivatives OX.

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Scheme 25: Hydrogenolyses of benzyloxy-substituted β-ketoenamides KE52 and KE54 to 1,2-diketone DK14 and to di...

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Scheme 26: Conversions of 2,4-dicyclopropyl-substituted oxazole OX7 into oxazole derivatives OX18–20 (PPA = po...

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Scheme 27: Syntheses of vinyl and ethynyl-substituted oxazole derivatives OX21 and OX23 and their palladium-ca...

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Scheme 28: Synthesis of C₃-symmetric oxazole derivative OX28 and the STM current image of its 1-phenyloctane s...

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Scheme 29: Condensation of 1,2-diketones DK with o-phenylenediamine to quinoxalines QU1–7 (CAN = cerium ammoni...

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Scheme 30: The LANCA three-component reaction leading to β-ketoenamides KE and the structure of functionalized...

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Review

Published 13 Mar 2019

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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

Beilstein J. Org. Chem. 2011, 7, 962–975, doi:10.3762/bjoc.7.108

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Scheme 1: Preparation of β-ketoenamides and subsequent cyclocondensation to 4-hydroxypyridines. a) Et₂O, −40 ...

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Scheme 2: Mechanistic rational for the formation of β-ketoenamides 16.

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Scheme 3: Reaction of proline derivative 45 and formation of β-ketoenamide 47 and enolester 48.

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Figure 1: ¹H NMR spectra of 49 and the mixture of diastereoisomers 49 and 49’.

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Scheme 4: Synthesis of pyrid-4-yl nonaflate 52.

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Scheme 5: O-Methylation of pyridine derivatives 22 and 30 followed by desilylation.

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Scheme 6: Formation of 5-alkoxypyrimidines from β-alkoxy-β-ketoenamides.

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Published 13 Jul 2011

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