Abstract Allyl halides react with elemental selenium in the N 2 H 4· H 2 O− KOH system to give diallyl chalcogenides and allyl propyl chalcogenides. The latter form only in the presence of oxygen when unsaturated intermediates CH 2= CHCH 2 YK (Y= S and Se), which are soluble in hydrazine hydrate, are hydrogenated with diimide.
