Synthesis of enantiopure 2-acyl azetidines and the application of amino alcohols derived therefrom in enantioselective catalysis
摘要:
Enantiopure 2-acyl azetidines were prepared in good yields from 2-cyano azetidines. The ketones produced were then stereo selectively reduced with sodium borohydride (with or without zinc bromide) or transformed into tertiary azetidinic amino alcohols by addition of phenyllithium. The latter compounds were found to be highly efficient catalysts for the enantioselective addition of diethylzinc to aldehydes, giving enantioselectivities up to 98%. (C) 2002 Elsevier Science Ltd. All rights reserved.
The reaction of an azetidine with a chloroformate can give either the dealkylated heterocycle or the ring-opened product (gamma-chloroamine), which can further cyclize to the oxazinanone. A general study of this underrated reaction was conducted and revealed that azetidines can undergo smooth nucleophilic ring-opening reactions to highly functionalized gamma-chloroamines in the presence of a variety of alkyl chloroformates under mild reaction conditions. Yields are usually good, and parameters governing this reaction were evaluated.