Nucleophilic Additions of Arylzinc Compounds to Aldehydes Mediated by CrCl₃:  Efficient and Facile Synthesis of Functionalized Benzhydrols, 1(3<i>H</i>)-Isobenzofuranones, Benzyl Alcohols, or Diaryl Ketones

Abstract

In the presence of a stoichiometric amount of CrCl3 and trimethylchlorosilane (TMSCl), nucleophilic addition of arylzinc compounds 1c−h to arylaldehydes 2a,b,g smoothly proceeded at room temperature to yield corresponding benzhydrols 4a−f in good yields. From arylzinc compounds 1a,b, 3-aryl-1(3H)-isobenzofuranones 3a−f were given by the CrCl3-mediated reaction with arylaldehydes 2a−f. Diaryl ketones 5a−e were obtained in good yields by the addition of excess amount of benzaldehyde as an oxidant to the resulting solution after the CrCl3-mediated reaction between arylzinc compounds 1c−g and arylaldehydes 2b,g was completed. In the nucleophilic additions of arylzinc compounds 1a,d,f to alkyladehydes 6b−f, the treatment of arylzinc compounds with CrCl3 was required prior to the addition of the aldehydes in order to prevent the fast protodezincation of arylzinc compounds by the enolizable aldehydes. In these CrCl3-mediated nucleophilic additions of arylzinc compounds to aldehydes, arylchromium(III) species are probably reactive intermediates