An exceptional P-H phosphonite: biphenyl-2,2'-bisfenchylchlorophosphite and derived ligands (BIFOPs) in enantioselective copper-catalyzed 1,4-additions.
Biphenyl-2,2'-bisfenchol (BIFOL) based chlorophosphite, BIFOP-Cl, exhibits surprisingly high stabilities against hydrolysis as well as hydridic and organometallic nucleophiles. Chloride substitution in BIFOP-Cl proceeds only under drastic conditions. New enantiopure, sterically demanding phosphorus ligands such as a phosphoramidite, a phosphite and a P-H phosphonite (BIFOP-H) are hereby accessible. In enantioselective Cu-catalyzed 1,4-additions of ZnEt2 to 2-cyclohexen-1-one, this P-H phosphonite (yielding 65% ee) exceeds even the corresponding phosphite and phosphoramidite.
Institut für Organische Chemie, Universität zu Köln, Greinstrasse 4, 50939 Köln, Germany. t.kop-weiershausen@uni-koeln.de
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Lex
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Neudörfl
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Goldfuss