New Monodentate P,C‐Stereogenic Bicyclic Phosphanes: 1‐Phenyl‐1,3a,4,5,6,6a‐hexahydrocyclopenta[<i>b</i>]phosphole and 1‐Phenyloctahydrocyclopenta[<i>b</i>]phosphole

Abstract

Abstract Racemic1‐phenyl‐1,3a,4,5,6,6a‐hexahydrocyclopenta[ b ]phosphole ( 4 ) was separated into enantiomerically pure 1‐phenyl‐1,3a,4,5,6,6a‐hexahydrocyclopenta[ b ]phosphole 1‐oxides [( R P )‐ 6 and ( S P )‐ 6 ] by an oxidative resolution procedure involving treatment of 4 with menthyl bromoacetate, crystallization of the resulting diastereoisomeric phosphonium bromides 8 , and stereoselective hydrolysis of the diastereomerically pure salts to the corresponding enantiomerically pure phosphane oxides. Stereoretentive reduction of P=O in ( R P )‐ 6 gave enantiomerically pure ( S P )‐ 4 . Hydrogenation of ( S P )‐ 6 and subsequent reduction of P=O afforded saturated 1‐phenyloctahydrocyclopenta[ b ]phosphole [( R P )‐ 5 ]. Monophosphanes ( S P )‐ 4 and ( R P )‐ 5 were tested as chiral ligands and catalysts in model asymmetric hydrogenation and C−C bond‐forming reactions. Enantioselectivities of up to 95% were observed. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2004)