On the mechanism of the Leuckart reaction.: Enantiospecific preparation of (1R,2R)- and (1S,2S)-N-(3,3-dimethyl-2-formylamino-1-norbornyl)acetamide

The Leuckart reaction of 2-norbornanone and (1R)-N-(3,3-dimethyl-2-oxo-1-norbornyl)acetamide ent-1b furnishes the expected N-(2-norbornyl)formamides 11 and ent-10 in good yield. Surprisingly, under the same reaction conditions, the (1R)-N-(7,7-dimethyl-2-oxo-1-norbornyl)acetamide 1a gives only 10, the enantiomeric form of the product obtained from ent-1b. An explanation of these results is given and a reaction mechanism, based on an unprecedented intramolecular transamidation, is proposed. (C) 1999 Elsevier Science Ltd. All rights reserved.