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).

中文翻译：

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还原非对映体的双（氧化膦）阻转异构体为一种非对映异构纯二膦：一种新的配体和一种新颖的配体制备设计

具有跨越C-5和C-5'的非手性桥的1,1'-联苯-2,2'-二膦烷形成为对映异构体的阻转异构体。以对映异构纯的形式获得它们需要解析其外消旋混合物或双（氧化膦）前体的外消旋混合物。具有跨越C-5和C-5'的同手性桥的1,1'-联苯-2,2'-二膦形成非对映异构体的阻转异构体。我们合成了第一种化合物1）选择性地和2）在热力学控制下—似乎是二膦合成中的首次利用。诱导选择性的步骤是高温还原两种非相互转化的双（氧化膦）阻转异构体（60:40的混合物）。它提供了所需的二膦烷非对映异构纯的（并且由于聚合产率为67％，因此不易对流）。在Tsuji-Trost烯丙基化反应中，这种二膦烷被证明是值得的，ee）。