Imine compounds five-membered rings

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. 

Relatively little data are available on sulfonamido derivatives of heterocyclic systems with five-membered rings. The tautomeric equilibrium between structures 222 and 223 has been shown to favor the imine form by about 10 1 by comparison of the ultraviolet spectrum of the parent compound with those of both methylated forms." ... 

With excess HFA a dioxolaneimine 99a is formed from a typical isonitrile reaction mentioned in previous sections. Acidification yields the unsubstituted five-membered ring 99, which is the parent compound of alkylated dioxolanes 99b-e available from isonitriles (R = Me, Et, t-Bu, c-CgHu) 111, 188). Whether the imine structure 99 or the ketone structure 101 has to be assigned to the hydrolysis product is not known. The Chapman rearrangement has been proved in the following system [Eq. (86)] 190). Treatment of 98 with strong bases like l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) yields a spirocyclic compound 100 with elimination of HCN the structure of 100 has been derived by spectroscopic methods 193). The reaction of 98 with HFA X HjO (91) in sulfuric acid produces a l,3-dioxolan-(4)one 112). 

HFA than of the imine. Attack on the metal atom of one molecule of HFA and imine is a prerequisite for the formation of five-membered rings. The lack of electron density in the HFA adduct inhibits ring expansion. According to these observations the displacement of triphenylphosphane by the more nucleophilic methyldiphenylphosphane promotes dioxolane formation 40). Platinaoxazolidines are available in both ways. No structural assignment has been given for the mixed compounds 182a, b 16). 

The reaction of a wide range of imines and other compounds containing the C=N moiety with 14 leads to the formation of azacyclopentenones, e.g. 337 (equation 100). Certain of the product heterocycles undergo oxidative dimerization Moreover, related five-membered ring systems result from analogous reactions of 14 with l-(r-pyrrolidinyl) acenaphthylene and thiazoline-5-thiones. ... 

Macrocyclic antibiotics also include a family of thiopeptides, of which thiostrepton (Figure 2.11) is the parent compound and the most complex member. Produced by Streptomyces azureus [59], thiostrepton includes 10 rings, 11 peptide bonds, extensive unsaturation, an imine functionality, a secondary amine, and 17 stereogenic centers [60] it also contains five thiazole rings and one quinoline nucleus. 

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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