Nitrogen-, Oxygen-, and Sulphur-containing Heterocycles

Relatively few papers have appeared concerning heterocycles which fall into this category, and only a small number of them merit discussion. Nitrile sulphides can be generated by thermal decarboxylation of l,3,4-oxathiazol-2-ones, and if this is done in the presence of dipolarophiles new heterocycles are formed. Reactions of this type are known to occur with alkenes, alkynes, and nitriles, and they have now been shown to occur with activated aldehydes and ketones. This provides a new route to 1,3,4-oxathiazolines (312) which were previously rather inaccessible. Silylated thioketones (313) are unstable but may be prepared and reacted in situ to provide routes to a variety of new heterocycles, depending upon the dipolar species used.  

A new method has been reported for the preparation of 1,2,3-benzoxathiazine-2,2-dioxides (314), Finally, 1,2,5-benzoxathiazepines (315) have been prepared through a novel rearrangement of the unstable adducts of sulphene with A -benzylidene-2-hydroxyanilides. The compound obtained was identical with that produced unambiguously by an alternative route. 

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