Reaction of allylic tin reagents with nitrogen heteroaromatics activated by alkyl chloroformates: regioselective synthesis of .alpha.-allylated 1,2-dihydropyridines and change of the regioselectivity depending on methyl substituents at the allylic moiety
A modular and efficient method for the synthesis of α-substituted 1,2-dihydroquinolines is described. Under mild metal-free conditions, readily available N-carbamoyl 1,2-dihydroquinolines undergo oxidative C–H alkynylation, alkenylation, and allylation with a range of potassium trifluoroborates using TEMPO oxoammonium salt as an oxidant.