Heterocyclics diazirines

Whereas oxaziridine and diaziridine were partial subjects of comprehensive theoretical studies on cyclic compounds (73MI50800), diazirine and some of its simple derivatives were the special target of quantum chemical investigations. Since diazirine, the lowest molecular weight heterocycle, has only five atoms and is of high symmetry, there was a chance for ab initio calculations, which followed some semiempirical studies. 

It is known that unsaturated three-membered nitrogen heterocycles display tautomerism involving nonaromatic and antiaromatic (i.e., Air systems) forms. In all cases, the nonantiaromatic tautomer is the most stable 1-azirine la and 1-diazirine 2a. Nonetheless, antiaromatic tautomers are known, for instance, triazirines 3. 

Hassner A (ed) (1984) Azetidines, /J-lactams, diazetidines, and diazirines. Small ring heterocycles. Part 2, The chemistry of heterocyclic compounds. Interscience, New York, p 589... 

The suggestion that three-membered heterocycles (362) are involved is illustrated by the postulated generation of derivatives of IH-diazirine (315 and 345), thiiren (328), thiazirin (337), and lif-triazirine (358). These three-membered heterocycles belong to the class of 4n-antiaromatic heterocycles their possible role as reaction intermediates is of general interest. There is, however, an interesting difference between the photochemistry of sydnones (Fig. 4) and meso-ionic l,2,4-triazol-3-ones (Fig. 6). In both cases IH- azirines (315 and... 

Simple heterocyclic compounds Three-membered heterocycles containing one heteroatom Oxiranes (epoxides), thiiranes (episulfides), aziridines Three-membered heterocycles containing more than one heteroatom Oxaziridines, dioxiranes, diazirines Four-membered heterocycles containing one heteroatom Oxetanes, thietanes, azetidines... 

Diazepines, 2,3-dihydro-, 17, 1 Diazirines, diaziridines, 2, 83 24, 63 Diazo compounds, heterocyclic, 8, 1 Diazomethane, reactions with heterocyclic compounds, 2, 245... 

Patent Diazirine Derivatives of Aromatic Heterocyclic Compounds... 

Three-membered heterocycles are an extensively studied class of compounds. Those with two nitrogen atoms, diazirine (unsaturated) (1) and diaziridine (saturated) (2) systems are fairly readily... 

Experimental methods have been remarkably useful especially in three-membered heterocycles. At the time of discovery of these compounds, mainly chemical methods were available to prove their structures, which yielded erroneous results. Experimental methods such as x-ray analysis, H NMR, 13C NMR, IR/Raman, UV, PES, and MS provided data on molecular geometry, bond connectivity, absolute configuration of the molecule, and configurational stability at nitrogen. Experimental data corrected and confirmed the chemical structures of title compounds. Complete experimental data from earlier studies on some diazirines and diaziridines, are provided and discussed with illustrations <84CHEC-I(7)195>. 

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