A highly stereoselective catalytic alkylation sequence for the synthesis of highly functionalized and versatile five-membered-ring compounds bearing all-carbon quaternary stereocenters was developed. Enantioselective desymmetrization of achiral cyclopentene-1,3-diones was thus executed by chiral Cu-phosphoramidite catalysts. A variety of complicated cyclopentane derivatives can be synthesized with
Lewis Acid Catalyzed Geminal Acylation Reaction of Ketones with 1,2-Bis[(trimethylsilyl)oxy]cyclobutene: Direct Formation of 2,2-Disubstituted 1,3-Cyclopentanediones
作者:Tracy J. Jenkins、D. Jean Burnell
DOI:10.1021/jo00085a041
日期:1994.3
Ketones reacted with 1,2-bis((trimethylsilyl)oxy)cyclobutene (1) under catalysis by boron trifluoride etherate to yield 2,2-disubstituted 1,3-cyclopentanedione products via silylated cyclobutanone intermediates in a two-step, one-pot process. In many instances addition of a small amount of water to the reaction medium after completion of the first step assisted the subsequent rearrangement to the product, such that reversion of the intermediate to the starting ketone became an insignificant process. Yields were best with cyclohexanones (>90%), but steric hindrance and conjugated double bonds reduced yields considerably.
The BF<sub>3</sub>·Et<sub>2</sub>O-Catalyzed Reaction of 1,2-Bis[(trimethylsilyl)oxy]cyclobutene and Analogues with Aromatic Ketones