Three-Component Coupling Reactions of Silylglyoxylates, Alkynes, and Aldehydes: A Chemoselective One-Step Glycolate Aldol Construction
摘要:
A single-pot three-component coupling reaction of silylglyoxylates (1), terminal alkynes, and aldehydes in the presence of ZnI2 and Et3N is presented. The products of the reaction, densely functionalized silyl-protected glycolate aldols (2), can be converted to the corresponding acetonides (3) in a one-pot deprotection/ketalization sequence. A variety of terminal alkynes and aldehydes can be successfully employed to give a range of highly functionalized, fully protected 1,2-diols in good yields and moderate diastereoselectivities. Mechanistic experiments suggest that the zinc acetylide reacts with the silylgyloxylate (1) in a chemoselective manner. Using an unoptimized (+)-N-methylephedrine and Zn(OTf)2 system, silyl-deprotected adduct 2 was formed in 64% ee and 89:11 dr.
Brook Rearrangement as Trigger for Carbene Generation: Synthesis of Stereodefined and Fully Substituted Cyclobutenes
作者:Fa-Guang Zhang、Ilan Marek
DOI:10.1021/jacs.7b04255
日期:2017.6.21
Through a sequence that can be performed in a single vessel, involving regio- and diastereoselective copper-catalyzedcarbomagnesiation of cyclopropenes, reaction with acylsilanes, and addition of THF as cosolvent, Brook rearrangement can be triggered to furnish a wide range of cyclobutenes with exceptional diastereoselectivity. Accordingly, stereodefined and highly substituted cyclobutenes with contiguous
Amide Enolate Additions to Acylsilanes: In Situ Generation of Unusual and Stereoselective Homoenolate Equivalents
作者:Robert B. Lettan、Chris V. Galliford、Chase C. Woodward、Karl A. Scheidt
DOI:10.1021/ja808811u
日期:2009.7.1
The synthesis of beta-hydroxy carbonyl compounds is an important goal due to their prevalence in bioactive molecules. A novel approach to construct these structural motifs involves the multicomponent reaction of acylsilanes, amides, and electrophiles. The addition of amide enolates to acylsilanes generates beta-silyloxy homoenolate reactivity by undergoing a 1,2-Brook rearrangement. These unique nucleophiles
Three-Component Coupling Reactions of Silyl Glyoxylates, Vinyl Grignard Reagent, and Nitroalkenes: An Efficient, Highly Diastereoselective Approach to Nitrocyclopentanols
作者:Gregory R. Boyce、Jeffrey S. Johnson
DOI:10.1002/anie.201003470
日期:2010.11.15
easy: A regio‐ and stereoselective three‐component couplingreaction generates functionalized (Z)‐silyl enol ethers through a vinylation/[1,2]‐Brook rearrangement/vinylogous Michael reaction cascade. These adducts can then undergo a diastereoselective deprotection/intramolecular Henry sequence to rapidly assemble densely functionalized nitrocyclopentanols with three contiguous stereocenters (see scheme;
快速简便:区域选择性和立体选择性三组分偶联反应通过乙烯基化/[1,2]-布鲁克重排/乙烯基迈克尔反应级联反应生成官能化的 ( Z )-甲硅烷基烯醇醚。然后,这些加合物可以进行非对映选择性脱保护/分子内亨利序列,以快速组装具有三个连续立体中心的密集官能化硝基环戊醇(参见方案;TES=三乙基甲硅烷基)。