Dilithiated (E)-N-isobutyl-4-tosyl-2-butenamide: An allyl sulfone dianion for the regiospecific gamma-functionalization of crotonamide dianion

(E)-N-Isobutyl-4-tosyl-2-butenamide (5b) (prepared from vinylacetic acid by stereoselective iodosulfonylation-dehydroiodination and further amidation) has been lithiated with two equiv of n-butyllithium at -78 degrees C in the presence of DMPU leading to the corresponding allyl dianion 6. This intermediate reacts with electrophiles (alkyl bromides, aldehydes and electrophilic olefins) regiospecific and stereoselectively at the gamma-position to afford gamma-substituted (E)-N-isobutyl-4-tosyl-2-butenamides 7. Desulfonylation of compounds 7 occurs stereoselectively to provide (E)-beta,gamma-unsaturated amides 9. This methodology has been applied to the synthesis of dienamides such as naturally occurring N-isobutyl-(2E,4E)-decadienamide (pellitorine). Copyright (C) 1996 Elsevier Science Ltd