Chiral copper complexes of BINOL- and TADDOL derived phosphorus amidites proved to be highly effective catalysts for the alkylation of alkynyl epoxides with dialkylzinc reagents. The corresponding alpha-allenol reaction products (S(N)2'-pathway) were obtained with good to excellent regio- and diastereoselectivity. The e.e. values obtained for this reaction were in the range of 26-38 %. A number of different Cu(II)-complexes were screened as possible catalysts and the results obtained indicate a complete control of the diastereoselectivity with an easy access to both enantioenriched syn and anti-alpha-allenols. (C) 1999 Elsevier Science Ltd. All rights reserved.
A new diastereo- and enantioselective copper-catalyzed conversion of alkynyl epoxides into alpha-allenic alcohols.
CROTTI, PAOLO;PINESCHI, MAURO;
1999-01-01
Abstract
Chiral copper complexes of BINOL- and TADDOL derived phosphorus amidites proved to be highly effective catalysts for the alkylation of alkynyl epoxides with dialkylzinc reagents. The corresponding alpha-allenol reaction products (S(N)2'-pathway) were obtained with good to excellent regio- and diastereoselectivity. The e.e. values obtained for this reaction were in the range of 26-38 %. A number of different Cu(II)-complexes were screened as possible catalysts and the results obtained indicate a complete control of the diastereoselectivity with an easy access to both enantioenriched syn and anti-alpha-allenols. (C) 1999 Elsevier Science Ltd. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
