The preparation, resolution and chemistry of 1-(3,6-dimethylpyrazin-2-yl)(2-naphthyl)diphenylphosphine, an axially chiral phosphinamine.

A five step synthesis of the title compound in good yield is described. The biaryl linkage was formed in a Pd-catalysed coupling of 2-chloro-3,6-dimet hylpyrazine 10 with 2-methoxy-1-naphthylboronic acid 9. Demethylation of th e product ether 11 afforded alcohol 12 which was converted into the corresp onding triflate 13 by treatment with triflic anhydride. A Ni-catalysed phos phinylation gave the required phosphinamine ligand 7 as a racemate. Diaster eomeric palladacycles 16, formed from 7 and (+)-di-mu-chlorobis[(R)-dimethy l(1-(1-naphthyl)ethyl)aminato-C-2,N]dipalladium (II) 85 were separated, aft er considerable effort, to give diastereomerically pure 7. Displacement of the resolving agent by reaction with 1,2-bis(diphenylphosphino)ethane gave enantiopure 7. At ambient temperature this ligand was found to racemise. (C ) 1999 Elsevier Science Ltd. All rights reserved.