Stereoselective Synthesis of 3-Substituted 4-(Formyloxy)-2-azetidinones by the Unusual Baeyer−Villiger Reaction of β-Lactam Aldehydes. Scope and Synthetic Applications
摘要:
The Baeyer-Villiger oxidation of 4-formyl-beta-lactams 1 with m-CPBA gave 4-(formyloxy) beta-lactams 2 in a simple, efficient, and totally stereoselective process. This reaction is one of the scarce examples of the preferred migration of a carbon moiety in an aliphatic aldehyde. The influence of the substituents at N1 and C3 of the four-membered ring in the Baeyer-Villiger rearrangement has been studied. Thus, alkyl, alkenyl, aryl, and alkyloxy 3-substituted-1-(p-anisyl)-2-azetidinone 1 form exclusively 4-(formyloxy) beta-lactams 2. Amide or acetoxy substituents at C3 of the four-membered ring produce mixtures of 4-(formyloxy) beta-lactams 2 and 4-carboxy beta-lactams 5. The exclusive formation of carboxy derivatives is observed sometimes for 1-alkyl-substituted-2-azetidinones 1. 4-(Formyloxy) beta-lactams 2 are suitable starting materials to prepare different 4-unsubstituted beta-lactams 9 using beta-hydroxy amides 8 as isolable intermediates. The overall transformation 4-formyl-2-azetidinone to 4-unsubstituted beta-lactam is an easy and convenient stereoselective route to these interesting types of compounds.
The unusual Baeyer-Villiger rearrangement of β-lactam aldehydes: Totally stereoselective entry to cis-3-substituted 4-formyloxy-2-azetidinones
作者:Benito Alcaide、Moustafa F. Aly、Miguel A. Sierra
DOI:10.1016/0040-4039(95)00492-u
日期:1995.5
Baeyer-Villigeroxidation of 4-formyl-β-lactams 1 with m-chloroperbenzoic acid in dichloromethane at room temperature is shown to be a convenient method for the preparation of 4-formyloxy-β-lactams 2. Some reactions of novel compounds 2 are also desrcribed.