THE PREPARATION OF NS-2,5-DIALKYLPYRROLIDINYLBENZYLDIPHENYLPHOSPHINES- NEW PHOSPHINAMINE LIGANDS FOR ASYMMETRIC CATALYSIS

The preparation of new phosphinamine ligands 3a, 3b, possessing an ena ntiopure trans-2,5-dialkylpyrrolidinyl unit is described. Of the three synthetic approaches investigated, two proved successful with similar overall yields of 50-60%. One approach forms the trans-2,5-dialkylpyr rolidine unit first and then the diphenylphosphine is introduced whils t the other reverses the order of introduction. In each approach the k ey step is the cyclocondensation of an amine with an enantiopure, dial kyl-substituted 1,4-diol cyclic sulfate. An X-ray crystal structure of the palladium dichloride complex 13 of ligand 3a is presented. (C) 19 98 Elsevier Science Ltd. All rights reserved.