In situ enzymatic screening (ISES) of P,N-ligands for Ni(0)-mediated asymmetric intramolecular allylic amination
作者:David B. Berkowitz、Weijun Shen、Gourhari Maiti
DOI:10.1016/j.tetasy.2004.06.052
日期:2004.9
An in situ enzymatic screening (ISES) approach to rapid catalyst evaluation recently pointed to Ni(0) as a new candidate transition metal for intramolecular allylic amination. This led to further exploration of chiral bidentate phosphine ligands for such transformations. Herein, a variety of P,N-ligands are examined for this Ni(0)-chemistry, using a model reaction leading into the vinylglycinol scaffold. On the one hand, an N,N-bis(2-diphenylphosphinoethyl)alkylamine ('PNP') ligand proved to be the fastest ligand yet seen for this Ni(0)-transformation. On the other, phosphinooxazoline (PHOX) ligands of the Pfaltz-Helmchen-Williams variety gave the highest enantioselectivities (up to 51% ee) among P,N-ligands examined. (C) 2004 Elsevier Ltd. All rights reserved.