Enantioselective Catalytic α-Alkylation of Aldehydes via an S_N1 Pathway

Primary aminothiourea derivatives are shown to catalyze enantioselective alkylation of α-arylpriopionaldehdyes with diarylbromomethane. Evidence for a stepwise, S_N1 mechanism in the substitution reaction induced by anion binding to the catalyst is provided by catalyst structure−activity studies, kinetic isotope effects, linear free-energy relationship studies, and competition experiments.