Diamidophosphite–oxazolines with a pyridine core in Pd-catalyzed asymmetric reactions
摘要:
We have designed and synthesized a small library of readily available P,N,N-diamidophosphite-oxazoline ligands containing 1,3,2-diazaphospholidine rings and a pyridine moiety. The use of these ligands provides up to 96% ee in Pd-catalyzed asymmetric allylations of (E)-1,3-diphenylally1 acetate; up to 80% ee in the Pd-catalyzed asymmetric alkylation of cinnamyl acetate with ethyl 2-oxocyclohexane-1-carboxylate and up to 94% ee in the Pd-catalyzed desymmetrization of N,N'-ditosyl-meso-cyclopent-4-ene-1,3diol biscarbamate. The influence of the structural modules, such as the nature of the phosphorus containing ring or pyridine substituent as well as of the addition of zinc(II) 5,10,15,20-tetraphenylporphyrin on the catalytic activity and enantioselectivity is discussed. (C) 2016 Elsevier Ltd. All rights reserved.