Lactam acetals Reformatsky reaction

Condensation reactions of simple carboxylic acids with imines are of intense interest because of their applications to 3-lactam synthesis. Activation of the carboxylic acid derivative is accomplished by preforming the enolate in situ or by using a silyl ketene acetal derivative with Lewis acid catalysis. The first example of an enolate-imine condensation of this type can be attributed to Gillman and Speeter, who in 1943 reported the synthesis of 3-lactams from Reformatsky reagents and Schiff bases. Subsequently, other workers have investigated the mechanism and syn-anti selectivity of this reaction. A review of these studies by Evans et al. covering work through 1980 has appeared in their review, Stereoselective Aldol Condensations . ... 

In this context the Reformatsky type reaction of Gilman and Specter between a-bromoesters and imines, the lithium enolate-imine condensation and the use of silyl ketene acetals, boron enolates and tin(II) enolates have been successfully utilized in the synthesis of appropriately substituted P-lactams for carbapenem synthesis. 

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