Synthesis and reactions of l-azirines

Synthesis, of tetracyclic and penlacyclic condensed thiophene systems. 32, 127 Synthesis and reactions of l-azirines. 13, 45 Synthesis of heleroeycles through nucleophilic additions to acetylenic esters, 19, 279... 

Synthesis, set also Heterocyclic synthesis and biological activities of condensed heterocycloln.m-tj, b, or cjquinazolines. 52, I and reactions of l-azirines, 13, 45 of condensed l,2,4-triazolo[3,4-z)heterocycles, 49, 277 by ring-closure of o-substituted t-anilines, 14, 211... 

Coe, P.L. Cook, M.I. Reactions of tetrafluoroethene oligomers. Part 16. The synthesis and reactions of perfluoro[2,3-dimethyl-2-(3-methylpentan-3-yl)]-2/f-azirine a source of 2,3-bis(trifluoromethyl)aziridine derivatives. J. Chem. Soc., Perkin Trans. 1 2000, 1537. 

Copper-mediated synthesis of 1,4-diaryl-l,2,3-triazoles 97 from iV-tosylhydrazones 96 and aniline was reported (13AG(E) 13324). Cu(ll)-catalyzed domino reactions of 2ff-azirines with diazotetramic and diazotet-ronic acids yielded synthesis of 2-substituted-2H-l,2,3-triazoles (130BC5535). Photooxygenation of azidoalkyl furans provided an endo-peroxide intermediate which underwent [3+ 2] cydoaddition to give... 

An efficient synthesis of 2Ff-azirines 6 substituted with a phosphate group is described. Its key step is an alkaloid catalyzed Neber reaction of -ketoxime tosylates 5 (equation 3) . Similarly, azirines containing an ester group in position 2 were obtained from tosy-lated oximes . A novel approach to substituted 2Ff-azirines using benzotriazole (Bt) methodology was recently presented. The reaction of benzotriazole oxime tosylates formed from the oxime 7 and TsCl with aqueous KOH yielded 2-(benzotriazol-l-yl)-2H-azirines. 

Smith and Most13 developed a modified Neber reaction for the synthesis of aminoketones which was used successfully by Parcell for the synthesis of 3,3-dimethyl-2-phenyl-l-azirine (26).14... 

Another important application of DCN-sensitized photodissociation of strained ring compoimds has been demonstrated by Muller and Mattay [127] for synthesizing iV-substimted imidazoles (147) by the [3-l-2]-cycloaddition of the 2-azaallenyl radical cation (144), produced by the cleavage of corresponding radical cation from azirine (143), with imines. This strategy is further extended [128] for the synthesis of pyrrolophane 3,4-dimethyl ester (152) by the ring opening cycloaddition reaction of (148) with dimethyl acetylene dicarb-oxylate (Scheme 32). 

Like the pyrrole synthesis, the assembly of 4-methylene-3-oxa-l-azabicyclo[3.1.0]hexanes is likely triggered by the formation of O-vinyl oxime (detected by GLC and NMR). The deprotonation of O-vinyl oxime in a-position relative to the oxime function and the further intermolecular nucleophilic substitution of the vinyloxy group can lead to azirine A (Scheme 1.178). The latter reacts with acetylene (in the form of carbanion) to give acetylenic ethynyl aziri-dine B (the nitrogen analog of the Favorsky reaction), which is added to the third... 

The main example of a category I indole synthesis is the Hemetsberger procedure for preparation of indole-2-carboxylate esters from ot-azidocinna-mates[l]. The procedure involves condensation of an aromatic aldehyde with an azidoacetate ester, followed by thermolysis of the resulting a-azidocinna-mate. The conditions used for the base-catalysed condensation are critical since the azidoacetate enolate can decompose by elimination of nitrogen. Conditions developed by Moody usually give good yields[2]. This involves slow addition of the aldehyde and 3-5 equiv. of the azide to a cold solution of sodium ethoxide. While the thermolysis might be viewed as a nitrene insertion reaction, it has been demonstrated that azirine intermediates can be isolated at intermediate temperatures[3]. 

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