Thermal and photochemical studies of symmetrical and unsymmetrical dihydro-1,3,4-selenadiazoles

Abstract

The thermal and photochemical reactivities of very sterically hindered dihydroselenadiazoles were investigated. The symmetrical tied-back dihydroselenadiazoles (4)–(6), and unsymmetrical fenchane (1,3,3-trimethylnorbornane) derived dihydroselenadiazoles (10)–(12) proved to be relatively thermally stable and could be used as intermediates in the preparation of the symmetrical olefins (7)–(9) and fenchane-derived olefins (15)–(17). The di-t-butylmethylene-derived dihydroselenadiazoles (28)–(30) were isolable, but underwent complete retrocyclization on thermolysis. Photolysis of symmetrical and unsymmetrical dihydroselenadiazoles afforded the corresponding azines in good yield.