Synthesis of 1-methyl-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-lithiation and phosphinylation of the coupled heterocycle in the final step. Attempts to resolve the phosphine by previously described methods led to its immediate racemisation, also observed more slowly in the PdCl2 complex, for which the X-ray structure is described. The phosphinamine formed a cationic Pd(1,3-diphenylallyl) complex with high diastereoselectivity. By analysis of the solution stucture using NMR techniques, in comparison with the X-ray structure, some inferences about the mechanism of allylic alkylation with related heterotopic ligands can be drawn. (C) 1997 Elsevier Science Ltd.