The Protection and Deprotection of the Pyridine Nitrogen

Abstract

In the course of our synthetic studies in the alkaloid area, we wished to generate and make use of some N-unsubstituted dihydropyridines as synthetic intermediates. However it is well known² that only very powerful nucleophiles will add to pyridines to generate dihydropyridines and even then usually only pyridines bearing electron withdrawing groups give good yields. Further we expected that the secondary nitrogen of an N-unsubstituted dihydropyridine would lead to undesirable side reactions in our planned reaction sequence and in general be too unstable to handle efficiently.