31 research outputs found
Catalytic Enantioselective alpha-Arylation of Carbonyl Compounds
Enantioselective creation of benzylic quaternary centers still is a continuous challenge to many synthetic organic chemists. Among the existing methods for installation of this type of center, the direct asymmetric alpha-arylation of carbonyl compounds is very attractive due to the ready availability of the coupling substrates. Herein, we present some new tools to the catalytic asymmetric alpha-arylation of carbonyl compounds that overcame many of the drawbacks posted in previous methods for this type of reaction
An epoxide ring-opening approach for a short and stereoselective synthesis of icetexane diterpenoids
A new approach for the synthesis of the core skeleton of icetexane diterpenoids is presented and deals with an epoxide ring-opening reaction by metallated aromatic compounds. Employing this strategy, a short synthesis of an icetexane analogue of brussonol was achieved in just four steps from 2-allyl-cyclohexanone. (C) 2009 Elsevier Ltd. All rights reserved.FAPESPFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)CNPqConselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq
Preparation of alpha,beta-Unsaturated Diazoketones Employing a Horner-Wadsworth-Emmons Reagent
A new method for the preparation of alpha,beta-unsaturated diazoketones from aldehydes and a Horner-Wadsworth- Emmons reagent is reported. The method was applied to the short synthesis of two substituted pyrrolidines.FAPESP (Research Supporting Foundation of the State of Sao Paulo)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)CNPqConselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq
Organocatalytic Enantioselective Sulfa-Michael Additions to α,β-Unsaturated Diazoketones
Enantioselective sulfa-Michael additions to α,β unsaturated diazocarbonyl compounds have been developed. Quinine-derived squaramide was found to be the best catalyst to promote C-S bond formation in a highly stereoselective fashion for alkyl and aryl thiols. The easy-to-follow protocol allowed the preparation of 22 examples in enantiomeric ratios up to 97:3 and reaction yields up to 94%. The mechanism and origins of enantioselectivity were determined through density functional theory (DFT) calculations.</p
Preparation of <i>Z</i>‑α,β-Unsaturated Diazoketones from Aldehydes. Application in the Construction of Substituted Dihydropyridin-3-ones
The
stereoselective preparation of α,β-unsaturated
diazoketones with <i>Z</i> geometry is described from aldehydes
and a new olefination reagent. When prepared from amino aldehydes,
these diazoketones could be converted to substituted dihydropyridin-3-ones
in just one step, after an intramolecular N–H insertion reaction.
The straightforward synthesis of a natural trihydroxylated piperidine
demonstrates the utility of these unsaturated diazoketones for the
rapid construction of piperidines