Studies of the stereoselective allylation of chiral benzaldimine chromium tricarbonyl complexes

Highly stereoselective allylation of a series of chiral tricarbonylchromium benzaldimine complexes (2a–c) was achieved at −20°C and homoallyl amine complexes (4a–c) were isolated in good yields. In the case of homoallyl amine 4c, obtained in 75% d.e., the degree of stereoselection depends on the catalyst and the reaction conditions. The crystal structure of the major diastereoisomer of racemic 4c was determined by X-ray diffraction, which showed a (S,S) or (R,R) configuration, in agreement with the stereochemical model operating for the ortho-substituted tricarbonylchromium arene complexes. Furthermore, the new tricarbonylchromium complex of N-(2-methoxybenzyliden)diphenyl phosphinamide 3 was prepared. This substrate is a stable analog of the normally unviable ammonia imine.