Epimine 3.4- epimines

Epimines. Irradiation of nitroamines and cyanoamines in the presence of phenyliodine(III) diacetate and iodine generates an aminyl radical which undergoes intramolecular hydrogen abstraction to produce epimines. 

The direct aziridination of alkenes can be accomplished by several methods which involve the in situ generation of the epiminating intermediate from a variety of precursors. 

Neighboring group participation involving acylamino or acyloxy groups is common in nucleophilic substitution. For example, in the reaction of methyl 4,6-0-benzylidene-2-deoxy-2-benzoylamino-3-O-mesyl-a-D-altro-pyranoside 8 with NaOEt, no 3-0-ethoxy-mannoside derivative was obtained. Instead, oxazoline 9 and epimine 10 were identified in this reaction (O Scheme 5) [12]. This results from the l,2-tra 5 -diaxial relationship between the leaving... 

Betancor, C., Concepcion, J. I., Hernandez, R., Salazar, J. A., Suarez, E. Intramolecular functionalization of nonactivated carbons by amidylphosphate radicals. Synthesis of 1,4-epimine compounds. J. Org. Chem. 1983, 48,4430-4432. 

The course of ammonolysis of 111 is rather complicated, and the reaction results in a mixture containing 2,4-diamino-l,6-anhydro-2,4-dideoxy-j8-D-glucopyranose756 (154) (compare Ref. 513) and 1,6-an-hydro-3,4-dideoxy-3,4-epimino-/3-D-altropyranose756 (153) as the major products. This reaction course may be most satisfactorily explained by the sequence 111—>151 152, where 4-amino-1,6 2,3-dianhydro-4-deoxy-/3-D-mannopyranose (152) partly isomerizes (see Sect. VI,2) to the epimine 153, and partly reacts with ammonia to give740 the diamino derivative 154. 

The aziridine ring is more stable than the oxirane ring in alkaline solution, as demonstrated by the low reactivity in attempts to accomplish isomerization of the hydroxyepimines to amino epoxides in alkaline media at room temperature, which contrasts with the rapid epoxide migration (see Sect. V,2). Isomerization of hydroxyepimines occurs only at high temperatures, and leads finally to the formation of amino derivatives of 1,6-anhydrohexoses.379,740 For example, when 166 is heated in 5% potassium hydroxide, 2-amino-l,6-anhydro-2-deoxy-/3-D-mannopyranose (168) is formed as the main product this can be explained by transient formation of 2-amino-l,6 3,4-dianhydro-2-deoxy-/3-D-altropyranose (167), and its subsequent, diaxial hydrolysis.379 Compound 167 is probably in equilibrium with epimine 166. Acid hydrolysis of the aziridine ring in 153 also follows a diaxial mechanism, without scission of the 1,6-anhydride bond, to give 4-amino-l,6-anhydro-4-deoxy-)8-D-mannopyranose756 (177). 

Epimines 153, 166, and 173 are crystalline compounds which show a slightly positive reaction in the ninhydrin test, and give characteri-istic H-n.m.r. spectra closely resembling those of the corresponding dianhydro derivatives (see Sect. III). Their N-benzoyl derivatives display379 a carbonyl stretching absorption at —1690 cm-1, shifted to frequencies higher than those of the common benzamides. 

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