Abstract
Spontaneous and unassisted methylene insertions into S─Cl and Se─S, C─S and C─H bonds as well as S─S and Se─S cleavages, double methylene insertions, and a1, 3-addition to diazomethane, which have been observed in the unaided low temperature reactions of diazomethane with sulfenyl halides and dithio-selenide without the need for the photo-generated carbene moiety.