Nitrile imines five-membered rings

Likewise, trifluoromethyl-substituted nitrile imines [172] and nitnle oxides [173,174, 7 75] have been used to synthesize tnfluoromethyl substituted five-membered ring systems of the pyrazole, isomzole, isoxazohne, and 1,2,4-oxadiazole... 

Perfluoroalkyl-substituted nitriles react readily with various 1,3 dipoles, such as azomethine ylides [755,156,157],azometlune imines [158],diazoalkanes [759],azides [160 161,162], and nitrile ylides [163] to give stable five-membered ring systems (equation 37)... 

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. 

In the reaction of nitrile oxides with phosphine imines, the five membered ring compounds 142 dissociate already at room temperature to give carbodiimides. For example, reaction of benzonitrile oxide with PhN=P(OEt)3 affords diphenylcarbodiimide in 76 % yield. 

Nitrile imines have been added to 1,4-diazepines (246) (143,144), 1,2, 4-triazepines (247) (145), 1-benzazepines (248) (146), 1,4-benzodiazepines (249-251) (147-149), 1,5-benzodiazepines (252, 253) (X = NH) (143,150-153), 1,5-benzothiazepines (253) (X=S) (153). Interest in this area has been stimulated by the known pharmacological activity of many compounds with five-membered heterocyclic rings fused to a benzodiazepine skeleton. 

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