Rhodium-Catalyzed Isomerization of a Bis(secondary phosphine) to an Unsymmetrical Diphosphine via P–C Cleavage and P–P and C–H Bond Formation,Organometallics

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Rhodium-Catalyzed Isomerization of a Bis(secondary phosphine) to an Unsymmetrical Diphosphine via P–C Cleavage and P–P and C–H Bond Formation
Organometallics ( IF 2.5 ) Pub Date : 2017-08-28 00:00:00 , DOI: 10.1021/acs.organomet.7b00515
Perry M. Scheetz ₁ , David S. Glueck ₁ , Arnold L. Rheingold ₂

Affiliation

To develop Rh-catalyzed dehydrocoupling for stereocontrolled synthesis of P–P bonds, we prepared potential intermediates, chiral rhodium phosphine-phosphido complexes, and investigated their stoichiometric and catalytic transformations. Treatment of [Rh(diphos*)(COD)][X] with the bis(secondary phosphine) IsHPCH₂PHIs (1, Is = 2,4,6-(i-Pr)₃C₆H₂) gave the cations [Rh(diphos*)(IsHPCH₂PHIs)][X] (diphos* = (R,R)-Me-DuPhos (2), (R,R)-i-Pr-DuPhos (3), or (R,R)-Me-BPE (4); X = BF₄ or OTf) with high diastereoselectivity as single C₂-symmetric diastereomers. Deprotonation of 2–4 with NaN(SiMe₃)₂ yielded phosphine-phosphido chelates Rh(diphos*)(IsHPCH₂PIs) 5–7 with high diastereoselectivity. Thermolysis of 5–7 in toluene at 90 °C caused isomerization to give Rh(diphos*)(IsMeP-PIs) (8–10) as mixtures of diastereomers. Under catalytic conditions, Rh-DuPhos precursors slowly converted 1 to a mixture of diastereomers of its isomer, the unsymmetrical diphosphine IsHP-PMeIs (12). We propose a possible mechanism for the isomerization and discuss its relationship to dehydrocoupling catalysis.

中文翻译：

铑催化的双（仲膦）异构体通过P–C裂解，P–P和C–H键形成不对称二膦

为了开发用于P-P键立体控制合成的Rh催化的脱氢偶联，我们制备了潜在的中间体，手性铑膦-膦基复合物，并研究了它们的化学计量和催化转化。用双（仲膦）IsHPCH ₂ PHI （1，Is = 2,4,6-（i -Pr）₃ C ₆ H ₂）处理[Rh（diphos *）（COD）] [X]得到阳离子[Rh（diphos *）（IsHPCH ₂ PHIs ）] [X]（diphos * =（R，R）-Me-DuPhos（2），（R，R）-i -Pr-DuPhos（3）或（R，R）-Me-BPE（4）；X = BF ₄或OTf）具有高非对映选择性，作为单个C ₂对称非对映异构体。去质子化2 - 4用的NaN（森达₃）₂，得到膦膦螯合物的Rh（DIPHOS *）（IsHPCH ₂ PIS）5 - 7具有高非对映选择性。在90°C下甲苯中5 – 7的热解引起异构化，得到非对映异构体混合物的Rh（diphos *）（IsMeP-PIs）（8 – 10）。在催化条件下，Rh-DuPhos前体缓慢转化1到其异构体的非对映异构体混合物中，是不对称的二膦IsHP-PMeIs（12）。我们提出了一种异构化的可能机制，并讨论了其与脱氢偶联催化的关系。

更新日期：2017-08-29

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