Dimethyl cyclobutane, decomposition

Both cis- and frana-butene-2 are formed from each of the dimethyl-cyclobutanes. They are not however formed in equilibrium amounts. Further, more a -butene-2 than the equilibrium amoimt is formed in the decomposition of cis-l,2-dimethylcyclobutane. The fact that the cis- and cyclo-butanes, this does imply that either the lifetime of the free biradical is of the same magnitude as the time for one rotation of the groups in the biradical, or that the biradical is never strictly a free biradical . In either case the configmation of the reactant will, to some extent, determine the stereochemistry of the products. 

Thermal decomposition of cis- and frans-3,6-dimethyl-3,4,5,6-tetrahydropyridazines affords propene, cis- and frans-l,2-dimethylcyclobutanes and 1-hexene. The stereochemistry of the products is consistent with the intermediacy of the 1,4-biradical 2,5-hexadienyl. The results indicate that thermal reactions of cyclic azo compounds and cyclobutanes of similar substitution proceed with similar stereospecificity when compared at similar temperatures 79JA2069). 

As part of a study on 1,4-diradicals, various 3,4,5,6-tetrahydropyridazines were decomposed thermally to olefins and cyclobutane derivatives (see also Section III,G). The activation parameters were measured. The stereochemical paths of thermal and photochemical nitrogen extrusion from 3,4,5,6-tetrahydropyridazines have been reexamined and rationalized. Kinetic measurements of the decomposition of 3,6-dimethyl-... 

As part of a study on 1,4-diradicals, various 3,4,5,6-tetrahydropyridazines were decomposed thermally513-518 to olefins and cyclobutane derivatives (see also Section III,G). The activation parameters were measured.519,520 The stereochemical paths of thermal and photochemical nitrogen extrusion from 3,4,5,6-tetrahydropyridazines have been reexamined and rationalized.521 Kinetic measurements of the decomposition of 3,6-dimethyl-3,6-dicyano-3,4,5,6-tetrahydropyridazine have been made.522 Pyridazines with specific functional group orientation can be used as starting material for the preparation of various dienes (Scheme 11). For example, compound 232 is quantitatively transformed into trans,frans-2,4-hexadiene (233), whereas the trans isomer 234 affords exclusively the cis-trans product (235).523,524 1,2-Dimethyl-1,2,3,6-tetrahydropyridazine is thermally decomposed to give mainly trans-azomethane, with about 10% of the cis-isomer.525... 

---