Intermediates for the Degenerate and Productive Metathesis of Propene Elucidated by the Metathesis Reaction of (Z)-Propene-1-d1

Article abstract of DOI:10.1021/ja00242a028

Intermediates for productive and degenerate metathesis of propene were elucidated by using (Z)-propene-1-d1 on molybdenum oxide catalysts activated with SnMe4.Productive metathesis of (Z)-propene-1-d1 yielded 2-butene with cis:trans < 1 and ethylene-1,2-d2 with cis:trans=1 on the catalysts.This result suggests that the mono-methyl-substituted metallacyclobutanes have no preferential configuration, while the 1,2-dimethylmetallacyclobutanes prefer to take the trans configuration.Degenerate metathesis between (Z)-propene-1-d1 and propene-d6 yielded (E)-propene-1-h1 in 80 percent selectivity.On the basis of these results, the ethylidene species is deduced as the dominant intermediate for the degenerate metathesis of propene.It is assumed in a proposed mechanism that (1) the rate-determinig step for the productive metathesis is the reaction of propene with Mo=CH-CH3 and (2) the degenerate and productive metatheses of propene are competitive in the reaction of propene with Mo=CH-CH3, but they bring about no mutual inhibition, because the degenerate metathesis does not change the population of the Mo=CH-CH3 intermediate.