Synthesis of α-silylcarboxylic acids

Development of a Novel Method for Trimethylsilylation of Saccharides­

The trimethylsilyl (TMS) group is widely used in carbo­hydrate synthesis, although this protecting group is unstable and its post-synthetic purification challenging. The successful trimethylsilyl­ation of carbohydrates mediated by recyclable and efficient acidic catalyst PTA/HMDS and the novel reagent, TMSOAc (TEA/TMSOAc), under alkaline condition is reported. The advantages of these methods are that the reactions proceed in good to excellent yields without applying column chromatography for purification.

Enediolate-dilithium amide mixed aggregates in the enantioselective alkylation of arylacetic acids: structural studies and a stereochemical model

A combination of X-ray crystallography, (6)Li, (15)N, and (13)C NMR spectroscopies, and density functional theory computations affords insight into the structures and reactivities of intervening aggregates underlying highly selective asymmetric alkylations of carboxylic acid dianions (enediolates) mediated by the dilithium salt of a C2-symmetric chiral tetraamine. Crystallography shows a trilithiated n-butyllithium-dilithiated amide that has dimerized to a hexalithiated form. Spectroscopic studies implicate the non-dimerized trilithiated mixed aggregate. Reaction of the dilithiated amide with the dilithium enediolate derived from phenylacetic acid affords a tetralithio aggregate comprised of the two dianions in solution and the dimerized octalithio form in the solid state. Computational studies shed light on the details of the solution structures and afford a highly predictive stereochemical model.