2/7-Azirine dimethyl ester

An interesting application of PET mediated bond cleavage reaction from azirine 63 has been reported by Mattay et al. [67] for synthesizing N-substituted imidazoles (65) via the (3 + 2) cycloaddition reaction of resultant 2-azaallenyl radical cations with imines 64. Synthesis of pyrrolophane 3,4-dimethyl ester (68) has been reported recently [68] by the ring opening of 66 followed by inter-molecular cycloaddition with dimethyl acetylene dicarboxylate (67) as shown in Scheme 13. 

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). 

Benzonitrile isopropylide, generated from 2,2-dimethyl-3-phenyl-2//-azirine, undergoes a cycloaddition reaction to the ester carbonyl group of diethyl (ethoxycarbonyl)phosphonate to give the diethyl 5-ethoxy-2,2-dimethyl-4-phenyl-3-oxazolin-5-ylphosphonate in 96% yield. ... 

Isoxazoles. - Formation. The combined action of copper(II) nitrate and acetic anhydride on 1,2-diphenylcyclopropane leads to a mixture of 3,5 diphenylisoxazole and its 4-nitro-derivative. Dimethyl azidomaleate affords the azirine (324) on heating, whereas the azidofumaric ester yields the isoxazole (325). 5-Amino-4-ethylthio-3-methylisoxazole (326) is produced from the acrylonitrile derivative MeCBr=C(SEt)CN and hydroxyl-amine." ... 

Section II,C,3,a In the presence of Mo(CO)6, 2,2-dimethyl-3-phenyl-2f/-azirine reacts with alkynoic esters via an unusual cleavage of the C=N bond to give 2/f-pyrroles in low yield.145... 

Reactions of 2,3-di(methoxycarbonyl)-2/f-azirine with keto-stabilized and ester-stabilized ylides give, respectively, substituted pyrroles and iminophos-phoranes (76). A similar reaction of the ketene-stabilized ylide (77) with 3.3-dimethyl-2-phenyl-l-azirine forms the oxaphospholene (78). ... 

The previously unknown l,2,3,6-tetrahydropyrazin-2-ones (270) are easily prepared by mixing 2,2-dimethyl-3-phenylazirine (271) with the methyl esters of a-amino-acids. " Another example of the use of this azirine is seen in its reaction with ammonia to give the amino-pyrazine (272) in 72% yield (Scheme 107). ... 

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