Abstract: A highly stereoselective organocatalytic aalkylation 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, ...