Oxazol-4-imines

3-Oxazol-5-imines (A nhydro-5-amino-1,3-oxazolium Hydroxides) (80) 

A mechanism has been proposed32 involving a meso-ionic 1,3-oxazol-5-imine (miinchnone imine) intermediate for the acid-catalyzed forma- 

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The keten-imine PhCOCPh=C=NPh reacts with jV-phenylhydroxyl-amine to yield the isoxazole-imine (334), which spontaneously rearranges to the oxazole-imine (335) by way of an intermediate aziridine. ... 

More recently, Williams has described the one pot synthesis of 2-substituted oxazoles 11 by the thermolysis of triazole amides 9 the reaction does not proceed photo-chemically.<92TL1033> Although the reaction does not involve addition to a nitrile, it is an interesting application of a diazo compound since the proposed zwitterionic intermediate 10 is a resonance form of a diazo imine, so formally the reaction may be thought of as a thermal decomposition of a diazo imine (Scheme 6). 

The only examples of 1,2,4-trioxolanes containing A-linked substituents arise from photooxygenation of oxazoles. The endoperoxides thus produced are bicyclic, with a 1,2,4-trioxolane ring bridged by an imine moiety and are unstable at ambient temperature. They have been characterized at low temperature and thermal rearrangement is described in Section 4.16.5.1.1. 

Oxazol-4-imines (Anhydro-4-amino-l,3-oxazolium Hydroxides) (87)... 

Meso-ionic l,3-oxazol-4-imines (87) have not been isolated by basic treatment of the corresponding salts (88). These salts (88) are formed by acid-catalyzed cyclization of the nitriles (89). ... 

Oxazol-4-imines Anhydro-4-amino-l,2-oxazdlium Hydroxides) (370)... 

The formation of an A-tosyl derivative of a meso-ionic l,2-oxazol-4-imine (370) in solution is possible, but the product was not isolated. 

Cycloadditions have been carried out to 37/-indoles (222, 223) (125,126), N-arylmaleimides (224) (127,128), l,2), -azaphospholes (225) (129), 5(47/)-oxazo-lones (226) (130), and 4,5-dihydrooxazoles (230) (131). The primary cycloadducts from the reaction of oxazolones (e.g., 226 with diaryl nitrile imines), derived from tetrazoles in refluxing anisole, do not survive. They appear to lose carbon dioxide and undergo a dimerization-fragmentation sequence to give the triazole 228 and the diarylethene 229 as the isolated products (130). In cases where the two aryl substituents on the oxazole are not the same, then, due to tautomerism, isomeric mixtures of products are obtained. 

An oxazole substituted with a complex aminohydantoin side chain is described as a muscle relaxant. Imine formation between glyoxylic acid and aminohydantoin (38-1) results in the imino acid (38-2). Use of that intermediate to acylate the amine on 4-chloro-2 -aminoacetophenone (38-3) leads to the amide (38-4), which now includes a 1,4-dicarbonyl array. Treatment of the keto-amide with phosphorus... 

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