Bis phosphides

An interesting feature of the reactions of the bis(arsenide) (55) and the bis(phosphide) (58) is the stereoselective nature of many of their reactions with bis(electrophiles). Thus, except for (56 X = S), where a trace of the R, R ) diastereomer was evident, the reactions in each case afforded the... 

When the bis(phosphide) (58) was reacted with the arsenic substrate (61 X = AsMe and Y = Cl), the compound (60 X = PPh) was isolated as a mixture of diastereomers each of which had the (R, S ) relative configuration at phosphorus. Chromatographic separation of the mixture followed by fractional crystallization of the material in the major fraction gave a small quantity of a single diastereomer, m.p. 138.5-139.5 °C, in which the arsenic-znetAy/groups were believed to be trans to one another. 

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