945907-32-4Relevant articles and documents
Reducing Diastereomorphous Bis(phosphane oxide) Atropisomers to One Atropisomerically Pure Diphosphane: A New Ligand and a Novel Ligand-Preparation Design
Sartorius, Frank,Trebing, Marc,Brückner, Charlotte,Brückner, Reinhard
supporting information, p. 17463 - 17468 (2017/11/27)
1,1′-Biphenyl-2,2′-diphosphanes with an achiral bridge spanning C-5 and C-5′ form atropisomers that are enantiomers. Accessing them in an atropisomerically pure form requires resolving a racemic mixture thereof or of a bis(phosphane oxide) precursor. 1,1′-Biphenyl-2,2′-diphosphanes with a homochiral bridge spanning C-5 and C-5′ form atropisomers that are diastereomers. We synthesized the first compound of this kind 1) atropselectively and 2) under thermodynamic control—seemingly a first-time exploit in diphosphane synthesis. The selectivity-inducing step was a high-temperature reduction of two non-interconverting bis(phosphane oxide) atropisomers (60:40 mixture). It furnished the desired diphosphane atropisomerically pure (and atropconvergently because the yield was 67 %). This diphosphane proved worthwhile in Tsuji–Trost allylations, the Hayashi addition of phenylboronic acid to cyclohexenone, and the asymmetric hydrogenation of methyl acetoacetate (up to 95 % yield and 95 % ee).
