The b-regioselective hydroformylation of the vinylidenic olefins 2-phenylpropene 1a., 2-methylpropene 1b. and 2,3,3-trimethylbutene 1c. was investigated via deuterioformylation experiments w1008C, 100 atm, Rh4CO.12 x carried out at partial substrate conversion. The crude reaction mixtures were directly submitted to 2H NMR analyses. The results obtained allowed to conclude that whereas the primary rhodium–alkyl intermediate undergoes migratory insertion on CO, giving the corresponding linear aldehyde, the tertiary rhodium–alkyl intermediate, when it does form i.e., in the case of 1a and 1b but not in the case of 1c., undergoes b-hydride elimination exclusively, accounting for the almost complete b-regioselectivity.
Rhodium-catalyzed hydroformylation of vinylidenic olefins: the different behavior of the isomeric alkyl metal intermediates as the origin of the b-regioselectivity
LAZZARONI, RAFFAELLO;UCCELLO BARRETTA, GLORIA;
1999-01-01
Abstract
The b-regioselective hydroformylation of the vinylidenic olefins 2-phenylpropene 1a., 2-methylpropene 1b. and 2,3,3-trimethylbutene 1c. was investigated via deuterioformylation experiments w1008C, 100 atm, Rh4CO.12 x carried out at partial substrate conversion. The crude reaction mixtures were directly submitted to 2H NMR analyses. The results obtained allowed to conclude that whereas the primary rhodium–alkyl intermediate undergoes migratory insertion on CO, giving the corresponding linear aldehyde, the tertiary rhodium–alkyl intermediate, when it does form i.e., in the case of 1a and 1b but not in the case of 1c., undergoes b-hydride elimination exclusively, accounting for the almost complete b-regioselectivity.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
