Synthesis and Thermal Decomposition of cis-3,4,5,6-Tetrahydropyridazine-3,4-d2. Relative Rates of Rotation, Cleavage, and Closure for Tetramethylene

Article abstract of DOI:10.1021/ja00531a031

The stereospecific syntheses of cis-3,4,5,6-tetrahydropyridazine-3,4-d2 (6) and cis- and trans-cyclobutane-1,2-d2 are reported.The thermal decomposition of cis-3,4,5,6-tetrahydopyridazine (6) (gas phase, 439 deg C) affords 67.1 +/- 0.9percent cis-ethylene-1,2-d2, 16.1 +/- 0.8percent trans-ethylene-1,2-d2, 9.4 +/- 0.4percent cis-cyclobutane-1,2-d2, and 7.4 +/- 0.4percent trans-cyclobutane-1,2-d2.The relative rates of rotation, cleavage, and closure for this 1,2-diazene generated tetramethylene-d2 are k(cleavage)/k(closure) = 2.2 +/- 0.2 and k(rotation)/k(closure) = 12 +/- 3.An extra stereospecific cleavage component (46percent) superimposed on the 1,4-biradical pathway (54percent) from the parent tetrahydropyridazine was found, similar to that observed in the 3,4-dimethyl-3,4,5,6-tetrahydropyridazine thermal reactions.Finally, the experimental data fot the parent 1,4 biradical, tetramethylene, are compared to calculated values in the literature.