Synthesis and Reactivity of Medium-Bridged Twisted Lactams

Abstract

The research presented herein describes the development of synthetic methods to one-carbon bridged twisted amides and the study of properties of one-carbon bridged lactams. Initial investigations focused on electrostatic cation-pi and cation-n interactions as regiochemistry controlling feature of the intramolecular Schmidt reaction to provide access to one-carbon bridged amides. In cases where the reactive conformation of the azidohydrin intermediate is locked, the selectivity of the reaction depends on the electron density of an aromatic ring oriented in 1,3-diaxial relationship with regard to the diazonium cation. However, a placement of a heteroatom in the α-position to the ketone permits the synthesis of otherwise unsubstituted bridged amides from conformationally flexible ring systems. Also, described is the development of a general method of synthesis of one-carbon bridged amides relying on a transannular cyclization strategy. Next, experiments directed towards investigation of unusual properties of distorted amides are presented. One-carbon bridged lactams display superior to other bridged amides levels of hydrolytic stability. These lactams participate in a number of interesting and potentially useful reactions unknown to traditional amide bonds, including synthesis of remarkably stable tetrahedral intermediates and a direct conversion into bridged spiro-epoxyamines. The influence of the amide bond geometry on reactivity of distorted lactams is also discussed.