Asymmetric cyclization catalyzed by a chiral phosphoric acid–gold(I) hybrid complex as a multifunctional catalyst

Abstract

Abstract We herein report the development of a novel hybrid complex containing gold(I) and a chiral phosphoric acid moiety to generate a multifunctional catalyst. While the use of chiral phosphoric acid as a bifunctional catalyst is a common strategy in asymmetric organic synthesis, chiral phosphoric acid–transition metal hybrid complexes as multifunctional catalysts have not been investigated. Thus, we designed and synthesized a novel gold(I) hybrid complex as a multifunctional catalyst that promotes asymmetric catalytic reactions through multipoint nonclassical noncovalent interactions in substrates that lack classical hydrogen-bond donors. In addition, we demonstrate its usefulness as a multifunctional catalyst by successfully developing the first catalytic asymmetric synthesis of dihydrocyclohepta[b]indoles. Experimental and theoretical studies revealed that this asymmetric catalytic reaction involves the kinetic resolution of the reaction intermediate, and that the favored diastereomeric transition state for yielding enantiomeric products is formed through multipoint nonclassical noncovalent interactions originating from the acid–base nature of the chiral phosphoric acid moiety.