Tunable phosphinite, phosphite and phosphoramidite ligands for the asymmetric hydrovinylation reactions

Only a limited number of ligands have been successfully employed for the Ni-cataiyzed asymmetric hydrovinylation reaction. Diarylphosphinites, carrying beta-acylamino groups prepared from readily available carbohydrates, in conjunction with highly dissociated counteranions {1(3,5-(CF3)(2)C6H3,](4)B- or SbF6-], effect the hydrovinylation of vinylarenes under ambient pressure of ethylene with high enantioselectivity. Nitrogen substituents such as -COCF3 and COPh groups lead to isomerization of the primary products (3-arylbutenes) to Z- and E-2-aryl-2-butenes. In a prototypical synthesis of a 2-arylproionic acid, (S)-3-(4-bromophenyl)-1-butene (89% ee) has be transformed into (R)-ibuprofen by Ni-catalyzed cross-coupling with i-BuMgBr, followed by oxidation of the double bond with NaIO4 and KMnO4. Asymmetric codimerization of norbonene and ethylene using binaphthol-derived phosphoramidites as ligands gives 1: 1, 2:1 or polymeric adducts depending on the relative C011figUrations and nature of the BINAP and amine moieties. With one of the phosphoramidite-Ni complexes, counteranions BAr4-[Ar=3,5-(CF3)(2)C6H3] and SbF6-, which had been used interchangeably in other reactions, give either a 1: 1 4 adduct or a 2:1 adduct, respectively. (c) 2005 Elsevier Ltd. All rights reserved.