MECHANISTIC AND SYNTHETIC STUDIES IN CATALYTIC ALLYLIC ALKYLATION WITH PALLADIUM COMPLEXES OF 1-(2-DIPHENYLPHOSPHINO-1-NAPHTHYL)ISOQUINOLINE

The title complexes are highly reactive catalysts for the reaction between (E)-1,3-diphenyl-2-propenyl acetate and dimethyl malonate ion; the enantiomer excess varies between 67% and 98% depending on how the reaction is conducted, with the best result obtained in CH3CN at -13 degrees C in the presence of 15-crown-5. With 2-cyclohexenyl acetate the reaction was much slower and the best e.e. obtained was 67%. With 1,1,3-triphenyl-2-propenyl acetate, reaction was again much slower than in the first case, the best e.e. was 47%, and the configurational correlation between catalyst and reactant was in the opposite sense. Many of the trends can be satisfactorily rationalised by recourse to the NMR spectra of a series of Pd allyl complexes. In the case of the (E,E)-1,3-diphenylallyl complex, two diastereomers were observed and their configurations assigned with the aid of nOe experiments. The results are best interpreted if the reaction proceeds through a late transition-state with nucleophilic attack on the allyl trans- to the phosphorus of the ligand and preferentially on the predominant diastereomer.