Selenobenzophenone reacts as a diene with dimethylacetylenedicarboxylate (DMAD) to lead to dimethyl 1H-1-diphenylmethyl-1-phenyl-2-benzoselenopyran-3,4-dicarboxylate (5c) in moderate yield; the initial [4 + 2] cycloaddition is followed by the addition of another 1 mol equiv of selenobenzophenone. The reaction might proceed through carbene insertion of the primary cycloadduct. On the other hand, 4
The reaction of selenobenzophenones with alkyllithiums or Grignard Reagents exclusively affords symmetrical tetraarylethylenes as selenophilic products. The reaction might proceed through episelenide (selenirane) intermediates.
Reactions of selenobenzophenones with dimethylacetylenedicarboxylate or norbornadiene gave benzoselenapyranes or seven-membered cyclic selenides; these reactions might proceed through unusual type of cycloaddition reaction.
Selenabicyclo[2.2.1]heptenes reacted with elemental selenium to produce unusual bicyclic diselenides in 30-40% yield. The reaction of phosphonium ylides with excess of elemental selenium also afforded bicyclic diselenides in good yields. The reactions might proceed via biradical intermediates.