Head-to-tail homo- and heterodimerization of vinylamides by hidden proton catalysis

Chemoselective dimerization of vinylamides is reported. A number of vinylacylamides were shown to undergo stereoselective cationic intermolecular head-to-tail homodimerization. Correspondingly, chemoselective heterodimerization reactions readily afforded hydroalkenylation of vinylacylamide with vinylsulfonamide. Different mild methods for hidden proton catalysis were studied. The in situ generation of, e.g., HSbF6 from the [Au]SbF6–PhCtriple bond; length of mdashCH] catalytic systems was applied. Successful vinylacylamide head-to-tail dimerizations seem to be dependant on the ability of N–C–O acylamide electron delocalization, affording stabilized intermediates. In general, the reactions demonstrate the ability of vinylacylamides to effectively undergo hydroalkenylation to afford 1,3-N,N-functionalized (E)-but-1-ene products.