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A novel enantiopure salen ligand bearing a diphenylphosphine oxide on the 3-position of one aromatic ring was synthesized and combined with Ti(Oi-Pr)_4 as a monometallic bifunctional catalyst for asymmetric cyanosilylation reaction of aldehydes with tnmethylsilyl cyanide(TMSCN).The catalyst system exhibited excellent activity and moderate enantioselectivity.The addition of TMSCN to 4-nitrobenzaldehyde in the presence of 1 mol%catalyst loading could complete within 10 min at ambient temperature. An intramolecularly cooperative catalysis was observed in this system wherein the central metal Ti(Ⅳ) is suggested to play a role of Lewis acid to activate aldehydes while the appended diphenylphosphine oxide worked as Lewis base to activate TMSCN.
A novel enantiopure salen ligand bearing a diphenylphosphine oxide on the 3-position of one aromatic ring was synthesized and combined with Ti (Oi-Pr) _4 as a monometallic bifunctional catalyst for asymmetric cyanosilylation reaction of aldehydes with tnmethylsilyl cyanide (TMSCN). The catalyst system showed excellent activity and moderate enantioselectivity. The addition of TMSCN to 4-nitrobenzaldehyde in the presence of 1 mol% catalyst loading could complete within 10 min at ambient temperature. An intramolecularly cooperative catalysis was observed in this system where the central metal Ti (IV ) is suggested to play a role of Lewis acid to activate aldehydes while the appended diphenylphosphine oxide worked as Lewis base to activate TMSCN.