SYNTHESIS OF ETHYL-2-DIPHENYLPHOSPHINO-3-(1'-ISOQUINOLYL)INDOLE - AN EASILY RACEMISED LIGAND GIVING INSIGHTS INTO CATALYTIC ASYMMETRIC ALLYLATION

The synthesis of the title compound is described, involving 2-lithiati on and phosphinylation of the coupled heterocycle in the final step. A ttempts to resolve the phosphine by previously described methods led t o its immediate racemisation, also observed more slowly in the PdCl2 c omplex, for which the X-ray structure is described. The phosphinamine formed a cationic Pd(1,3-diphenylallyl) complex with high diastereosel ectivity. By analysis of the solution stucture using NMR techniques, i n comparison with the X-ray structure, some inferences about the mecha nism of allylic alkylation with related heterotopic ligands can be dra wn. (C) 1997 Elsevier Science Ltd.