Novel Chiral C2-Symmetric Bisimidazole-N-Oxides as Promising Organocatalysts for Enantioselective Allylation of Aromatic Aldehydes

A series of new, chiral Lewis bases containing imidazole-N-oxide moiety were tested for purposes of asymmetric catalysis. Bisimidazole-N-oxides derived from (1R,2R)- and (1S,2S)-trans-1,2-diaminocyclohexane were used as catalysts in the allylation reaction of aromatic aldehydes with allyltrichlorosilane, which yielded homoallyl alcohols in good yields and with enantioselectivity up to 80% cc. Screening of catalysts revealed that the type of substituents and their location in imidazole ring has a crucial influence on enantioselectivity of the addition process.