Scheme 1. General pathway for the Nef reaction.
Similar to many reversible processes, conversion of carbonyl derivatives to nitroalkanes is possible by exploiting a reversed pathway involving as preliminary step formation of oxime 3 followed by its oxidation to the final nitro compound 1. The latter process is far from being trivial since strong oxidizing agents must be employed under controlled conditions in order to avoid side reactions leading to rearranged products.9,10
For this reason, a complementary strategy for the preparation of nitroalkanes employs oxidative processes carried out on primary amines.11 The aim of this review is to provide up-to-date information on the nitro to carbonyl conversions that appeared after our previous report which dates back to 2004.4 Special emphasis will be given to new synthetic methods to achieve this conversion and those processes in which the Nef reaction is included in tandem or cascade transformations.