(Z)-selective β-bromination of N-formyl-α,β-dehydroamino acid esters

Article abstract of DOI:10.1016/0040-4020(96)00209-8

Stereoselective β-bromination of N-formyl-α,β-dehydroamino acid esters 5 was investigated. A reaction of 5 with NBS afforded α-bromo-N-formylimines 10 which successively isomerized to give β-bromo-N-formyl-α,β-dehydroamino acid esters 4. The migration of the double bond of the intermediates 10 with bulky substituents at the β-position resulted in highly stereoselective formation of (Z)-4, while that of the substrates with less bulky substituents proceeded non-stereoselectively. A mechanism of the stereoselective bromination was proposed on the basis of semiempirical calculations using AM1.