Kinetics and mechanism of organocatalytic aza-Michael additions: direct observation of enamine intermediates
Chem. Commun., 2012, 48, 4504-4506 published on 13.03.2012
The imidazoles 1a–g add to the CC-double bond of the iminium ion 2 with rate constants as predicted by the equation log k = sN(N + E). Unfavourable proton shifts from the imidazolium unit to the enamine fragment in the adduct 3 account for the failure of imidazoles to take part in iminium-activated aza-Michael additions to enals.