Chiral copper complexes of 2,2'-binaphthyl-based phosphorus amidites are shown to be highly effective catalysts for the conjugate addition of dialkylzinc reagents to vinyloxiranes. The corresponding allylic alcohol reaction products (S(N)2'-pathway) were obtained with moderate to high regioselectivity. Both direct- (S(N)2-pathway) and conjugate-opening addition (S(N)2'-pathway) seem to proceed with complete anti stereoselectivity. The enantioselectivity of these addition reactions according to a kinetic resolution protocol turned out to be high (>90% ee) with 1,3-cyclohexadiene and 1,3-cycloheptadiene monoepoxides. (C) 1998 Elsevier Science Ltd. All rights reserved.
Catalytic enantioselective carbon-carbon bond formation by addition of dialkylzinc reagents to cyclic 1,3-diene monoepoxides.
CROTTI, PAOLO;PINESCHI, MAURO;
1998-01-01
Abstract
Chiral copper complexes of 2,2'-binaphthyl-based phosphorus amidites are shown to be highly effective catalysts for the conjugate addition of dialkylzinc reagents to vinyloxiranes. The corresponding allylic alcohol reaction products (S(N)2'-pathway) were obtained with moderate to high regioselectivity. Both direct- (S(N)2-pathway) and conjugate-opening addition (S(N)2'-pathway) seem to proceed with complete anti stereoselectivity. The enantioselectivity of these addition reactions according to a kinetic resolution protocol turned out to be high (>90% ee) with 1,3-cyclohexadiene and 1,3-cycloheptadiene monoepoxides. (C) 1998 Elsevier Science Ltd. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
