Addition of organocopper reagents to cyclic sulfites or carbonates of γ,δ-dihydroxy (E)-α,β-enoates
摘要:
Reaction of cyclic sulfites or carbonates of gamma,delta-dihydroxy (E)-alpha,beta-enoates with R2Cu(CN)Li2, BF3; RCu(CN)Li, BF3 (R = Me-,n-Bu-)afforded either diastereoselective S(N)2' products or reductive elimination product depending on reaction conditions. Addition of R2Cu(CN)Li2, BF3 (R = Me-, n-Bu-) to cyclic sulfite (1) or cyclic carbonate (3) (inverse addition) afforded highly regio-, (E)-stereo- and diastereoselectively alpha-alkylation products (6 and 8). By using this methodology, (2S, 5S)-trans-2-methyl-5-hexanolide, the pheromone of the carpenter bee Xylocopa hirutissima was synthesized.
Asymmetric addition of (triisopropylsilyl)acetylene to α,β,γ,δ-unsaturated carbonyl compounds took place in the presence of a cobalt/Duphos catalyst to give the 1,6-addition products in high yields with high regio- and enantioselectivity.
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.
Catalytic Enantioselective 1,6-Conjugate Addition of Grignard Reagents to Linear Dienoates
作者:Tim den Hartog、Syuzanna R. Harutyunyan、Daniel Font、Adriaan J. Minnaard、Ben L. Feringa
DOI:10.1002/anie.200703702
日期:2008.1
De novo synthesis of galacto-sugar δ-lactones via a catalytic osmium/palladium/osmium reaction sequence
作者:Md. Moinuddin Ahmed、George A. O’Doherty
DOI:10.1016/j.tetlet.2005.03.029
日期:2005.4
A highly efficient route to various 1,5-galacto-sugar lactones from dienoates has been developed by using three catalytic reactions. These reactions include (i) an enantioselective osmium-catalyzed dihydroxylation, (ii) a regio- and diastereoselective palladium-catalyzed pi-allyl alkylation with p-methoxyphenol for alcohol differentiation and protection, and (iii) a diastereoselective dihydroxylation that can be improved using matched emantioselective osmium-catalyzed dihydroxylation condition. (c) 2005 Elsevier Ltd. All rights reserved.
De Novo Enantioselective Syntheses of <i>Galacto</i>-Sugars and Deoxy Sugars via the Iterative Dihydroxylation of Dienoate
作者:Md. Moinuddin Ahmed、Bryan P. Berry、Thomas J. Hunter、Dennis J. Tomcik、George A. O'Doherty
DOI:10.1021/ol050044i
日期:2005.2.1
[GRAPHICS]An efficient route to various sugar lactones has been developed. Key to the overall transformation is the sequential osmium-catalyzed dihydroxylation of 2,4-dienoates. The simplest (one-step/racemic) example of this reaction occurs when the dihydroxylation is performed with aqueous NMO in MeOH. When the first dihydroxylation is performed using the AD-mix procedure, an enantioselective variant results. When a matched AD-mix procedure is used for the second dihydroxylation, an exceedingly diastereo- and enantioselective synthesis of galacto-1,4-lactone results.