α-Substituent effect on olefination of ester carbonyl groups with ynolates
摘要:
In the olefination reaction of ester carbonyl with ynolate, an alpha-hetero (N, O, S)-substituent on the substrates was found to markedly improve the yields of tetrasubstituted olefins, even though it was sterically hindered. The alpha-substituent effect may be due to several factors including the addition based on the polar Felkin-Anh model and restricted conformation of the initial adducts. (C) 2013 Elsevier Ltd. All rights reserved.
An efficient synthetic method for the preparation of multisubstituted furans, thiophenes, and pyrroles using ynolates was developed. This novel formal [4 + 1] annulation by C2-C3 and C3-C4 bond formations includes cycloaddition, cyclization, decarboxylation, and dehydration as key steps.
We have developed the E-selective olefination of ester carbonyls to afford tetrasubstituted, functionalized olefins and the C-S insertion of thiol esters to give beta-keto thiol esters via ynolates.
[2+2] and [2+4] Type Cycloadditions of Isocyanates with Ynolates
Ynolates react with isocyanates to give azetidine-2,4-diones via a [2 + 2] type cycloaddition. The [4 + 2] type cycloaddition proceeds in the reactions of vinyl isocyanates with ynolates to provide 2-pyridones.