Formation of Highly Substituted Tetrahydropyranones: Application to the Total Synthesis of Cyanolide A
摘要:
A new tetrahydropyranone synthesis has been developed that leads to cis-2,6-disubstituted 3,3-dimethyltetrahydropyran-4-one rings by condensation of an aldehyde and a hydroxy silyl enol ether. The reaction works with a variety of aldehydes to produce the tetrahydropyranone products in moderate to high yields. This new method was applied to the enantioselective synthesis of cyanolide A and its aglycone.
Reported herein is a visible‐light‐mediated radical approach to the α‐alkylation of ketones. This method exploits the ability of a nucleophilic organocatalyst to generate radicals upon SN2‐based activation of alkyl halides and blue light irradiation. The resulting open‐shell intermediates are then intercepted by weakly nucleophilic silyl enol ethers, which would be unable to directly attack the alkyl
In this work, we disclose a new catalytic and highly chemoselective cross-Claisen condensation of esters. In the presence of TBSNTf2 as a non-metal Lewis acid, various esters can undergo cross-Claisen condensation to form β-ketoesters which are important building blocks. Compared with the traditional Claisen condensation, this process, employing silyl ketene acetals (SKAs) as carbonic nucleophiles
Cooperative organocatalysis of Mukaiyama-type aldol reactions by thioureas and nitro compounds
作者:Konstantin V. Bukhryakov、Victor G. Desyatkin、Valentin O. Rodionov
DOI:10.1039/c6cc01984f
日期:——
A unique organocatalytic system for Mukaiyama-type aldol reactions based on the cooperative action of nitrocompounds and thioureas has been identified. This system is compatible with a wide range of...
Reversal of Chemoselectivity in Organotin Lewis Acid-Catalyzed Reaction of Ketene Silyl Acetal with Aldehyde and α-Enal
作者:Jianxie Chen、Junzo Otera
DOI:10.1055/s-1997-715
日期:——
The organotin Lewis acid-catalyzed reaction of ketene silyl acetal with aldehydes results in reversal of chemoselectivity: α-enals react preferentially or exclusively in competition with an alkanal or even aromatic aldehydes.
Mukaiyama–Michael addition of a ketenesilylacetal on a cyclic α,β-unsaturated ketone, followed by the addition of a glyoxylic, aromatic or heteroaromatic imine. According to the nature of the silyl group the adducts resulting from this tandem process are isolated as ketones or as enoxysilanes. The presence of a coordinating group on the imine increases the rate of the reaction.