Five-membered rings nitrile imine cycloadditions

Reaction kinetics for the interaction of 5-alkyliminothiatriazoles 52 or 58 with heterocumulenes, nitriles, ketones, imines, or other dipolarophiles a=b show that the decomposition of the thiatriazole is bimolecular, and new heterocyclic five-membered rings 71 are formed (Scheme 15). The term masked 1,3-dipolar cycloaddition was used by L abbe and co-workers for this type of reaction <1978JOC4951>, the thioimidate function being the masked 1,3-dipole. The reaction is thought to involve a thiapentalenic intermediate 70 with hypervalent sulfur. The product 71 is itself a masked dipole and often further reactions take place. 

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