Asymmetric synthesis of a chiral diarsine ligand via a cycloaddition reaction between 3,4-dimethyl-1-phenylarsole and diphenylvinylarsine

The organopalladium complex containing ortho-metallated (S)-[1-(dimethylamino)ethyl]naphthalene as a chiral auxiliary has been successfully employed to promote the asymmetric cycloaddition reaction between 3,4-dimethyl-1-phenylarsole and diphenylvinylarsine. In the intramolecular cycloaddition reaction, a pair of separable diastereomeric palladium complexes was obtained in the ratio of 6:1. The chiral naphthylamine auxiliary could be removed chemoselectively from the template by treatment with HCl and subsequently NaI to generate the neutral diiodo complex [(As–As)PdI2]. Treatment of the diiodo complex with KCN gave the enantiomerically pure As–As bidentate ligand in quantitative yield. In contrast to the reported similar P–P and As–P analogues, both arsenic donors in the diiodo complex could be readily eliminated to produce a structurally novel dimetallic complex.

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C40H42As2ClNO4Pd[α]D20 = −91.8 (c 0.49, CH2Cl2)Absolute configuration: 1R, 2S,4R,7R,αS

C26H26As2I2Pd[α]D20 = −78.6 (c 0.14, CH2Cl2)Absolute configuration: 1R, 2S,4R,7R

C27H29As2[α]D20 = −81.7 (c 6.16, CDCl3)Absolute configuration: 1R, 2S,4R,7S