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

Article abstract of DOI:10.1016/0040-4039(96)00936-7

(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°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 γ-position to afford γ-substituted (E)-N-isobutyl-4-tosyl-2-butenamides 7. Desulfonylation of compounds 7 occurs stereoselectively to provide (E)-β,γ-unsaturated amides 9. This methodology has been applied to the synthesis of dienamides such as naturally occurring N-isobutyl-(2E,4E)-decadienamide (pellitorine).