Published as sub project in J.H. MacMillan, Ph.D. Thesis, Northeastern University, 1970.
Several examples of thermal rearrangements of 1,5-hexadiynes have appeared in the recent literature and the products reported include bisallenes, dimethylenecyclobutenes, benzenes and fulvene. A number of intermediates have been proposed to account for the particular products observed. This study concerns the vapor phase thermolysis of 1,5-hexadiyn-3-ol (1) at 350 degrees which affords methylenecyclobutene carboxaldehyde (11), presumably from its enolic dimethylenecyclobutene progenitor, and phenol. The presence of the hydroxy group facilitates the reaction pathway leading to aromatization. Methyl substitution in I results in formation of appropriate methyl derivatives of II and indicates the absence of hydroxy migration or carbon skeletal rearrangements in the formation of phenol. Prismane or benzvalene intermediacy can be ruled out on the basis of this data. A mechanistic scheme will be presented to correlate these results and those previously appearing in the literature. Abstracts, Houston A.C.S. Meeting, Feb. 1970, No. ORGN 50.