2//-Azirine, 3-phenyl-, reaction with

Azirine, formation, 56, 372 2W-Azirine-2-acrylates, 3-phenyl-reaction with formamidine, 57, 62, 63 guanidine, 57, 63 hydrazine, 57, 62... 

Azirine, trans-2-methyl-3-phenyl-racemization, 7, 33, 34 1-Azirine, 2-phenyl-reactions, 7, 69 with carbon disulfide, S, 153 1-Azirine, 3-vinyl-rearrangements, 7, 67 Azirines, 7, 47-93 cycloaddition reactions, 7, 26 fused ring derivatives, 7, 47-93 imidazole synthesis from, 5, 487-488 photochemical addition reactions to carbonyl compounds, 7, 56 photolysis, 5, 780, 7, 28 protonated... 

A narrow range of 2-phenyl-1-azirines underwent photodriven reactions with alkoxycarbenes to give AT-vinylimidates, in a process probably related to the above reactions (Table 24) [126]. 

The presence of a 2-substitutent in 3-phenylazirines (17, R —H in Scheme 21) modifies the mode of reaction with molybdenum carbonyl.47 In contrast to pyrazine formation for (17, R =H see Section V,C,2), the alkenyl azirine (18, Scheme 22) is transformed in excellent yield into 2-phenyl-5-carboxy-methylpyrrole. This product probably arises by intramolecular cyclization within an intermediate dienylnitrene intermediate, and related reactions have been devised to synthesize isoxazoles (see Section IV,E,2) and pyrazoles (see Section IV,D,1).47 The molybdenum carbonyl-promoted formation of 2,5-disubstituted pyrroles47 has analogy in uncatalyzed thermal, but not photochemical decomposition of 3-phenyl-2//-azirine 2-acrylate.49... 

Sato et al. observed that the reaction of 2-phenyl-1-azirine with acid chlorides and anhydrides in the presence of triethylamine gives the oxazole directly.57 They have reported that azirines also react with carboxylic anhydrides to give oxazoles (136).57 Aziridine (135) is suggested as a likely intermediate in the reaction of acetic anhydride with azirine (42a), since carrying out the reaction at lower temperature and for a shorter reaction time gave a compound to which they assigned structure 135. 

Phenyl-l-azirine (42a) reacts with acetophenone in the presence of the dimethylsulfinyl carbanion to give 2,4-diphenylpyrrole (150).65 This reaction probably involves initial attack of the enolate anion on the carbon-nitrogen double dond, to give intermediate 147 and 148 which ring-opens to 149 and loses hydroxide ion giving pyrrole (150). A similar reaction of ethyl benzoylacetate with 2-phenyl-l-azirine yields 3-benzoyl-4-phenyl-2-oxopyrroline (151). 

Nair has recently observed a similar reaction with 2-phenyl-3-methyl- and 2-phenyl-3,3-dimethyl-l-azirine.69... 

Activation of 3-alkyl and 3-phenyl-2H-aziiines by Lewis acids also promotes their participation in hetero Diels-Alder reactions with a variety of dienes. This methodology circumvents the previous requirement of needing an electron-withdrawing carboxyl moiety at the 3-position of the 2H-azirine ring (01TL9289). Thus, the reaction of 2H-azirine 125 with Danishefsky s diene gave the endo-cycloadduct 126... 

The thermocatalytic Rh(ll) decomposition of diazo malonate in the presence of 3-phenyl-2/7-azirine 772d was proposed to give rise to an azirinium ylide 803 <2004TL6003>. This reactive ylide is preferentially transformed into 2-azabuta-l,3-diene derivative 804 or, with excess diazo compound, via reaction with the Rh-carbenoid, forms the 3,4-dihydro-2/7-pyrrole derivative 806 via intermediate 805 (Scheme 196). 

Diphenyl-l-azirine (29) and benzyne yield the 1 1 adduct 31 (50%) and 1 2 adduct 32 (14%).34 The formation of these indoles can be explained by assuming 1,2-cycloaddition of benzyne, reorganization of the strained intermediate 30, and some N-phenylation of 31 by further reaction with benzyne. 

Several three-membered ring nitrogen heterocycles, such as azirines, aziridines, di-aziridines and oxaziridines, undergo [3+2] cycloaddition reactions with isocyanates. For example, irradiation of 3-phenyl-2//-azirines 363 affords the benzonitrile ylides 364 which react with aryl isocyanates to give the oxazolines 365, resulting from addition across the C=0 bond of the isocyanate... 

The photochemical behavior of the isomeric 3-methyl-2-phenyl-2-allyl-l-azirine (66) system was also studied. Irradiation of (66) in cyclohexane gave a quantitative yield of azabicyclohexenes (67) and (68). Control experiments showed that (65) and (66) were not interconverted by a Cope reaction under the photolytic conditions. Photocycloaddition of (66) with an added dipolarophile afforded a different 1,3-dipolar cycloadduct from that obtained from (65). The thermodynamically less favored endo isomer (68b) was also formed as the exclusive product from the irradiation of azirine (66b). 

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