H-2 NMR INVESTIGATION OF THE RHODIUM-CATALYZED DEUTERIOFORMYLATION OF1,1-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 degrees 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 labe led normal aldehyde arising from this substrate. The above compounds h ave been detected by H-2 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 beta-hydride elimination only with out formation of the branched aldehyde.