AbstractA highly stereoselective organocatalytic α‐alkylation of 2‐arylacetaldehydes with a commercially available carbenium tetrafluoroborate is described. The stereoselective alkylation was carried out in acetonitrile/water, under air in the presence of a commercially available imidazolidinone (MacMillan’s catalyst). Key intermediates for the synthesis of bisabolanes were obtained through a simple chemistry. In particular a direct, enantioselective and facile synthesis of (R)‐(−)‐curcumene is described.magnified image
A chiral cyclohexadiene-based dihydrogen surrogate can distinguish between the enantiotopic faces of benzylic carbenium ions (see Scheme). No covalent interactions are required but instead dispersion controls the facial discrimination as verified by computations.