Four-membered heterocyclic compounds containing high coordinate group 16 elements

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Title compounds containing tetracoordinate sulfur, pentacoordinate sulfur, tetracoordinate selenium and tetracoordinate tellurium together with oxygen or nitrogen were successfully synthesized as stable compounds. Some compounds have the Martin ligand that is well-known to stabilize such high coordinate main group compounds, while others have another four-membered ring. X-ray crystallographic analyses revealed that the compounds have distorted trigonal bipyramidal (TBP) or pseudo TBP structures. In marked contrast to group 13–15 element analogues, which afford the corresponding olefins on heating, their thermolyses gave the corresponding oxiranes or an aziridine except for a few 1,2-oxachalcogenetanes, suggesting the possibility that these compounds are intermediates of the Corey–Chaykovsky reaction of chalcogen ylides with carbonyl compounds or imines. The stereochemistry (retention of configuration) of some oxirane formation reactions as well as compounds synthesized by other groups is also described.