Addition and cyclization reactions in the thermal conversion of hydrocarbons with an enyne structure, 7 - Cycloisomerization of 1-phenyl-1-buten-3-yne to naphthalene via cinnamylidene carbenes - A complex reaction involving 1,2-C switches and 1,2-styryl migrations

The thermal conversion of [4-C-13,4-D]- (1) and [4-C-13]-1- phenyl-1-buten-3-yne (7) has been studied in a quartz tubular reactor at 650 degrees C (1, in the presence of N-2 and N-2/toluene, respectively) and at 600 and 620 degrees C (mixture of 1 and 7, in N-2 only) at a reaction time of approximately 0.3 s. The liquid pyrolyzates were analyzed spectroscopically. By means of a special calculation method reported recently, the naphthalene isotopomers formed by reaction pathways other than those proceeding via cinnamylidene carbenes were arithmetically eliminated and the reaction events proceeding via carbene intermediates were mechanistically analyzed. The result of this analysis undoubtedly suggests a complex reaction in which the rates of the partial reactions may be placed in the following order: 1,2-D(H) >> 1,2-styryl > 1,6-C,H.