BETA-HYDRIDE ELIMINATION AND REGIOSELECTIVITY IN THE RHODIUM-CATALYZED HYDROFORMYLATION OF OPEN-CHAIN UNSATURATED ETHERS

The influence of the temperature on the regioselectivity in the rhodiu m-catalyzed hydroformylation of ethyl vinyl ether and ethyl allyl ethe r has been investigated in the range 20-120 degrees C. For both substr ates, the amount of branched aldehyde decreases as the temperature inc reases, this effect being more pronounced for ethyl allyl ether than f or ethyl vinyl ether. The H-2 NMR investigation of the deuterioformyla tion products obtained at partial conversion, with particular attentio n to the unconverted substrates, points out the different behavior of the metal. alkyl intermediates: at room temperature their formation is irreversible, at high temperature it becomes reversible for both isom ers in the case of ethyl vinyl ether, but only for the branched one in the case of ethyl allyl ether. These results fully account for the ob served influence of the temperature as well as the substrate structure on the regioselectivity.