Mild and Efficient Methods for the Reductive Cleavage of Nitrogen-Oxygen Bonds

Abstract

In connection with synthetic programs underway in our laboratory, in particular the development of synthetic methods based on oxidative cycloadditions of hydroxamic acids with 1,3-dienes,¹ with lycoricidine² (la) and narciclasine³ (lb) as representative target structures, we required a reductive cleavage of N—O bonds in the resulting Diels-Alder adducts. Application to the target structures of interest required a mild and specific method, which would leave carbon-carbon double bonds and (amide) carbonyl groups intact, and which would not disturb potentially acid sensitive functionality. In response to these criteria we have developed new methods for accomplishing the desired objectives, which are easily carried out and generally give high yields of reduced products. These methods considerably extend the scope and power of oxidative cycloadditions of hydroxamic