A simple procedure for the preparation of enantiopure ethyl α-hydroxyalkyl ketones
摘要:
Amides derived from pyrrolidine and methyl (S)-lactate, methyl (S)-2-hydroxy-3-phenylpropanoate, or methyl (S)-2-hydroxy-3-methylbutanoate, after O-benzylation and O-silylation have been treated with EtLi or EtMgCl under suitable conditions, to give excellent overall yields of enantiopure ethyl ketones. The chelating ability of alpha-OBn amides (and even of alpha-O-TBS amides, which has been demonstrated by NMR to be better than that of N-OMe amides) accounts for the performance of the approach. (C) 1997 Elsevier Science Ltd.
Simple and Efficient Preparation of Ketones from Morpholine Amides
作者:R. Martín、P. Romea、C. Tey、F. Urpí、J. Vilarrasa
DOI:10.1055/s-1997-1050
日期:——
Morpholine-derived amides react with RMgX to give the corresponding ketones in good yield. The mild conditions required and low cost of starting materials make this method very appealing for large scale preparations.
Aldol-like reactions of titanium enolates derived from α-OH, α-OBn, and α-OTBS ketones with a series of aldehydes have been studied. In sharp contrast to the O-benzyl derivatives, the TBS-protected ketones lead to excellent yields and selectivities ( ratios from 30:1 to >95:1) even for the lactate-derived substrate (2-tert-butyldimethylsilyloxy-3-pentanone).
The acylation reaction of organolithium reagents with pyrrolidine-derived α-benzyloxy and α-silyloxy carboxamides provides a simple and high-yielding method for the preparation of enantiopure α-benzyloxy and α-silyloxy ketones.