²H NMR Investigation of the Rhodium-Catalyzed Deuterioformylation of 1,1-Diphenylethene: Evidence for the Formation of a Tertiary Alkyl−Metal Intermediate

Abstract

Rhodium-catalyzed deuterioformylation of 1,1-diphenylethene at partial substrate conversion (15 and 34%) at 100 °C and 100 atm (CO/D2 = 1:1) gives, in addition to the expected 3,3-diphenylpropanal-1,3-d2, the monodeuterated olefin 1,1-diphenylethene-2-d1 and the labeled normal aldehyde arising from this substrate. The above compounds have been detected by 2H NMR analysis of the crude reaction mixtures. These findings demonstrate that a tertiary alkyl−rhodium intermediate is formed, under hydroformylation conditions, in a larger amount than the normal isomer, but it undergoes β-hydride elimination only without formation of the branched aldehyde.