title: Highly active, regioselective, and enantioselective hydroformylation with Rh catalysts ligated by Bis-3,4-diazaphospholanes.
abstract: Azines made by the reaction of hydrazine with ortho-formylbenzoic acid react with 1,2-diphosphinobenzene and either succinyl chloride or phthaloyl chloride in ca. 30% yield to give rac-bis-3,4-diazaphospholanes bearing benzoic acid groups in the 2 and 5 positions. Condensation of the benzoic acid functionalities with enantiomerically pure amines affords diastereomeric benzoamides which can be separated by flash chromatography. Application of the resolved bis-3,4-diazaphosholanes to Rh-catalyzed enantioselective hydroformylation of styrene, allyl cyanide, and vinyl acetate under mild pressures (20-500 psig of CO/H2) and temperatures (40-120 degrees C) reveals high activities and selectivities for all three substrates. At 60 degrees C and 500 psig syn gas, the best ligand provides outstanding regio- and enantioselectivities (styrene, 89% ee, b:l = 30:1; allyl cyanide, 87% ee, b:l = 4.8:1; vinyl acetate, 95% ee, b:l = 40:1) while achieving turnover frequencies of ca. 3000 h-1.
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Clark
authors.forename: Clark R
authors.initials: CR
authors.lastname: Landis
authors.forename: Susan L
authors.initials: SL
authors.lastname: Freed
authors.forename: Jerzy
authors.initials: J
authors.lastname: Klosin
authors.forename: Khalil A
authors.initials: KA
authors.lastname: Abboud