Reaction of Ketone Hydrazones with Diselenium Dihalides: Simple Synthesis of Δ3-1,3,4-Selenadiazolines and 2,5-Diarylselenophenes

Sterically congested cis- and trans-Δ 3 -1,3,4-selenadiazolines were isolated by one-pot reactions of ketone hydrazones with diselenium dibromide, which suggested the in situ formation of selone and diazoalkane intermediates. The thermolysis of these compounds gave symmetrical olefins, whereas oxidation afforded the corresponding azines. The reaction of acetophenone hydrazones with diselenium dibromide afforded 2,5-diarylselenophenes in moderate yields. The reaction proceeded through selone intermediates.