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

Rhodium-catalyzed deuterioformylation of 1,1-diphenylethene at partial substrate conversion (15 and 34%) at 100 °C and 100 atm (CO/D 2 = 1:1) gives, in addition to the expected 3,3-diphenylpropanal- 1, 3 - d 2, the monodeuterated olefin 1,1-diphenylethene- 2 - d 1 and the labeled normal aldehyde arising from this substrate. The above compounds have been detected by 2 H 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.