Nucleophilic additions of arylzinc compounds to aldehydes mediated by CrCl₃: Efficient and facile synthesis of functionalized benzhydrols, 1(3H)- isobenzofuranones, benzyl alcohols, or diaryl ketones

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.