Stereodivergent Aminocatalytic Synthesis of <i>Z</i>
- and <i>E</i>
-Trisubstituted Double Bonds from Alkynals
作者:Leyre Marzo、Javier Luis-Barrera、Rubén Mas-Ballesté、José Luis García Ruano、José Alemán
DOI:10.1002/chem.201603437
日期:2016.11.7
A highly diastereoselectivesynthesis of trisubstituted Z‐ or E‐enals, which are important intermediates in organic synthesis, as well as being present in natural products, is described using different alkynals and nucleophiles as starting materials. Diastereocontrol is mainly governed by the appropriate catalyst. Therefore, those reactions controlled by steric effects, such as the Jørgensen–Hayashi's
C5‐disubstituted Meldrum's acid precursors were shown to be a useful platform for the synthesis of an array of 3‐alkylated dihydrocoumarins with up to 93:7 er, thanks to an enantioselective domino cyclization‐decarboxylative‐protonation reaction triggered by an unprecedented benzhydryl‐derived cupreine organocatalyst. This cyclization sequence was extended to an emerging organocatalytic decarboxylative‐chlorination
Development of Pharmaceutical Drugs, Drug Intermediates and Ingredients by Using Direct Organo-Click Reactions
作者:Dhevalapally B. Ramachary、Mamillapalli Kishor、Y. Vijayendar Reddy
DOI:10.1002/ejoc.200701014
日期:2008.2
two-carbon homologation through cascade O/H/H reactions of aldehydes 1, Meldrum's acid (3c), Hantzsch ester (4) and acetic acid/triethylamine in ethanol has been demonstrated. Additionally, we have developed a green synthesis of the highly substituted 1,2,3-triazole 17 from simple substrates through a two-step combination of olefination/hydrogenation/alkylation and Huisgen cycloaddition reaction sequences
Multi-catalysis cascade reactions based on the methoxycarbonylketene platform: diversity-oriented synthesis of functionalized non-symmetrical malonates for agrochemicals and pharmaceuticals
作者:Dhevalapally B. Ramachary、Chintalapudi Venkaiah、Y. Vijayendar Reddy、Mamillapalli Kishor
DOI:10.1039/b901652j
日期:——
In this paper we describe new multi-catalysis cascade (MCC) reactions for the one-pot synthesis of highly functionalized non-symmetrical malonates. These metal-free reactions are either five-step (olefination/hydrogenation/alkylation/ketenization/esterification) or six-step (olefination/hydrogenation/alkylation/ketenization/esterification/alkylation), and employ aldehydes/ketones, Meldrum's acid, 1,4-dihydropyridine/o-phenylenediamine, diazomethane, alcohols and active ethylene/acetylenes, and involve iminium-, self-, self-, self- and base-catalysis, respectively. Many of the products have direct application in agricultural and pharmaceutical chemistry.
An asymmetric organocatalysed decarboxylative protonation reaction allowed a straightforward synthesis of α-substituted isoxazolidin-5-ones from readily available 5-substituted Meldrum's acids. This process is initiated by an anionic formal (3+2) cycloaddition–fragmentation, generated in-situ from a sulfone-amide precursor which also served as a latent source of proton.