Asymmetric Formal <i>trans</i>-Dihydroxylation and <i>trans</i>-Aminohydroxylation of α,β-Unsaturated Aldehydes via an Organocatalytic Reaction Cascade
study demonstrates the first formal asymmetric trans-dihydroxylation and trans-aminohydroxylation of alpha,beta-unsaturated aldehydes in an organocatalytic multibond forming one-pot reactioncascade. This efficient process converts alpha,beta-unsaturated aldehydes into optically active trans-2,3-dihydroxyaldehydes and trans-3-amino-2-hydroxyaldehydes with the aldehyde moiety protected as an acetal. The
The addition of nucleophiles like lithium ester enolates 6 to oxiranecarbaldimines 1 leads to new oxiranyl-functionalised β-lactams 7 in excellent enantio- and diastereoselectivity. A simple one-pot procedure affords β-lactams (azetidin-2-ones) with three or four neighbouring stereogenic centres and unlike preference. Products resulting fromoxirane ring-opening reactions were not observed. An enantiomerically
Study on the stereochemical control of dihydroxylation of vinyl epoxides and their derivatives
作者:Giuliana Righi、Emanuela Mandic’、Gaia Clara Mercedes Naponiello、Paolo Bovicelli、Ilaria Tirotta
DOI:10.1016/j.tet.2012.02.029
日期:2012.4
The results obtained from a study on the stereochemical control in the dihydroxylation of the double bond of vinyl epoxides and their derivatives (bromo derivatives, azido derivatives and vinyl aziridines) are presented herein. A significant diastereoselectivity was observed for the bromo derivatives, azido derivatives and N-protected vinyl aziridines, whereas vinyl epoxides and unprotected vinyl aziridines
Palladium-catalyzed stereospecific epoxide-opening reaction of γ,δ-epoxy-α,β-unsaturated esters with an alkylboronic acid leading to γ,δ-vicinal diols with double inversion of the configuration
A palladium-catalyzed stereospecific epoxide-opening reaction of gamma,delta-epoxy-alpha,beta-unsaturated esters with an alkylboronic acid leading to gamma,delta-vicinal diols is described, which proceeds with retention of the configuration, i.e., via two consecutive S(N)2 processes, to afford the corresponding gamma,delta-cyclic boronates in high yields.
Direct organocatalytic asymmetric epoxidation of α,β-unsaturated aldehydes
作者:Henrik Sundén、Ismail Ibrahem、Armando Córdova
DOI:10.1016/j.tetlet.2005.10.128
日期:2006.1
The organocatalyticasymmetric epoxidation of α,β-unsaturatedaldehydes with peroxides or sodium percarbonate is presented. Chiral pyrrolidine derivatives, proline and amino acid derived imidazolidinones mediate the asymmetric epoxidation of α,β-unsaturatedaldehydes. For example, commercially available protected α,α-diphenyl-2-prolinol catalyzes the asymmetric formation of 2-epoxy-aldehydes in 81–95%