First Isolation of cis- and trans-1,3,4-Selenadiazolines from Pivarophenone Hydrazones

Sterically congested cis- and trans-1,3,4-selenadiazolines were isolated by one-pot reaction of pivalophenone hydrazones with diselenium dibromide, which suggested in situ formation of selenoketone and diazoalkane intermediates. Thermolysis of these compounds gave symmetrical olefins, whereas oxidation afforded the corresponding azines.