New, optically active phosphine oxazoline (JM-Phos) ligands: Syntheses andapplications in allylation reactions

Three different syntheses of the phosphine oxazoline systems 1 are presente d. Two of these approaches are divergent routes designed to involve an adva nced intermediate that can be transformed into several different end-produc ts. The third is a shorter route specifically designed to facilitate prepar ations of these systems on a larger scale using minimal functional group pr otection. Overall, eight different phosphine oxazolines were prepared. Thes e were screened in several palladium-mediated allylation reactions. They pr oved to be most useful for asymmetric alkylation of 3-acetoxy-1,3-diphenylp ropene and less suitable/effective for the more challenging substrates (a p entenyl derivative and a cyclohexenyl system). X-ray crystallographic analy sis of the complex [(eta (3)-PhCHCHCHPh)Pd(1a)][PF6] led to the conclusion that the origins of asymmetric induction in these systems might be indirect ly attributed to interaction of the oxazoline-phenyl substituent with the p alladium and with an allyl-phenyl substituent. Finally, data is presented f or allylation of a silylenolate of an N-acyl oxazolidinone; excellent enant ioselectivities and yields were obtained.