3- phenyl azirine

The known thermal and photochemical decomposition of a-azidostyrene (153), which gave quantitative yields of phenyl azirine (154) via a vinyl nitrene, > has been used by a Japanese group who have carried out the decomposition in the presence of acrylonitrile and methyl acrylate, giving functionalized vinyl aziridines e.g. 155) a- and j3-azido styrenes and 2-azido-rra j -butene (156) were examined. 

Important synthetic paths to azirines and aziridines involve bond reorganization, or internal addition, of vinylnitrenes. Indeed, the vinylnitrene-azirine equilibrium has been demonstrated in the case of trans-2-methyl-3-phenyl-l-azirine, which at 110 °C racemizes 2000 times faster than it rearranges to 2-methylindole (80CC1252). Created in the Neber rearrangement or by decomposition of vinyl azides, the nitrene can cyclize to the p -carbon to give azirines (Scheme 4 Section 5.04.4.1). 

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). 

The 1-azirines obtained from the vapor phase pyrolysis of 4,5-disubstituted 1-phthalimido-1,2,3-triazoles (157) have been found to undergo further thermal reactions (71CC1S18). Those azirines which contain a methyl group in the 2-position of the ring are cleaved to nitriles and phthalimidocarbenes, whereas those azirines which possess a phenyl substituent in the 2-position rearrange to indoles. 

The reaction of 2-phenyl-l-azirine (201) with benzoic acid gaveN-benzoylphenacylamine (204) (67BCJ2938). The overall mechanism of the reaction involves initial protonation on nitrogen followed by addition of the nucleophile to the azirinium ion and finally ring opening. 

Azirines react with enolate anions. Initial nucleophilic attack on phenyl 1-azirine by the enolate anion derived from acetophenone gives intermediate (223) which undergoes 1,2-bond cleavage, cyclization and hydroxyl group elimination to give pyrrole (226). 

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... 

Isoxazole, 3-chloro-5-hydroxymethyl-oxidation, 6, 27 Isoxazole, 4-chloromethyI-reactions, 6, 53 Isoxazole, 5-chloro-3-phenyl-reactions, 6, 58 Isoxazole, 3-cyano-reactions, 6, 30 Isoxazole, diacyl-synthesis, 6, 79 Isoxazole, 3,4-dialkyl-synthesis, 6, 83 Isoxazole, 3,5-dialkyl-synthesis, 6, 83 Isoxazole, 4,5-dialkyl-synthesis, 6, 83 Isoxazole, 3,5-diamino-2-amino-l-azirines from, 7, 89 Isoxazole, 3,5-diaryl-synthesis, 6, 63 Isoxazole, 2,5-dihydro-synthesis, 6, 79 Isoxazole, 4,5-dihydro-dehydrogenation, 6, 4... 

PHENYL-2H-AZIRINE-2-CARB0XALDEHTDE [2ff-Azirine-2-cu boxaldeh7de, 3-phenyl-]... 

C. 2-(Dimethoxymethyl)-3-phenyl-2H-azirine. The crude product (71-75 g., 0.32-0.34 mole) obtained from Part B is heated at reflux in 11. of chloroform in a 2-1., round-bottomed flask for 12 hours (Note 9). The solvent is removed with a rotary evaporator and the crude residue... 

The aldehyde functionality present in 3-phenyl-2H-azirine-2-carbox-aldehyde reacts selectively with amines and with Qrignard and Wittig reagents to give a variety of substituted azirines. These azirines have been used, in turn, to prepare a wide assortment of heterocyclic rings such as oxazoles, imidazoles, pyrazoles, pyrroles, and benzazepins. ... 

In the photochemical isomerization of isoxazoles, we have evidence for the presence of the azirine as the intermediate of this reaction. The azirine is stable and it is the actual first photoproduct of the reaction, as in the reaction of r-butylfuran derivatives. The fact that it is able to interconvert both photochemically and thermally into the oxazole could be an accident. In the case of 3,5-diphenylisoxazole, the cleavage of the O—N bond should be nearly concerted with N—C4 bond formation (8IBCJ1293) nevertheless, the formation of the biradical intermediate cannot be excluded. The results of calculations are in agreement with the formation of the azirine [9911(50)1115]. The excited singlet state can convert into a Dewar isomer or into the triplet state. The conversion into the triplet state is favored, allowing the formation of the biradical intermediate. The same results [99H(50)1115] were obtained using as substrate 3-phenyl-5-methylisoxazole (68ACR353) and... 

Wittig reaction of 3-phenyl-2//-azirine-2-carbaldehyde (1) with [3-(methoxycarbonyl)prop-2-enylidene]triphenylphosphorane (2) in hot benzene yields a mixture of methyl 7-phenyl-l//-azepine-2-carboxylate (3) and the 2//-azirine4.13 Diene 4 is extremely heat sensitive and isomer-izes on standing at room temperature to the lf/-azepine 3 (see also Section 3.1.1.5.7.). 

Photolysis of (Z)-3-phenyl-2-(2-phenylvinyl)-2//-azirine (1) in benzene solution yields 1-phenyl-3//-2-benzazepine (2) in excellent yield.39 However, the stereochemistry of the alkenyl side chain and the solvent used are important in determining the outcome of the reaction. For example, the E-isomer of the 2//-azirine 1 on photolysis in benzene solution yields 2,3-diphenyl-pyrrole as the major product (85 %) the pyrrole is also obtained on heating the Z- or E-isomer in benzene solution. In contrast, irradiation of the Z-isomer in methanol yields only acyclic products. 

Another photochemical ring enlargement leading to a 1,3-oxazepine is the formation of 2-phenyl-l,3-oxazepine (13) by irradiation of 4-phenyl-2-oxa-3-azabicyclo[3.2.0]hepta-3,6-diene (11).12 It is proposed that the process involves the azirine 12 as an intermediate. 

A refluxing solution of 3-phenyl-2//-azirine (0.468 g, 4 mmol) in toluene (10 mL) was treated with 3,6-diphcnyl-l,2.4.5-tetrazine (0.702 g, 3 mmol) in toluene (10 mL) and the solution was boiled under reflux for 22 h. On cooling, the mixture deposited an orange precipitate, which was filtered off and washed with pentane. Further product was obtained from the mother liquor by chromatography (silica gel). The combined solids were recrystallized (benzene/pentane) to give the product yield 0.664 g (68%) orange plates mp 210 C. 

A similar but asymmetric variant of the reaction, involving the radical addition of alkyl iodides and trialkylboranes to chiral azirine esters derived from 8-phenyl-menthol and camphorsultam, in the presence of a Cu(i) catalyst, has subsequently been reported [64]. The diastereoselectivity of the addition is variable (0-92% de)... 

Desilylation of a,P-aziridinylsilanes is a route to nonstabilized metalated aziridines. Treatment of 254 with CsF in the presence of PhCHO furnished substituted aziridine 255 in good yield (Scheme 5.65). Interestingly, the isomeric aziridine 256 gave azirine 257 on treatment with CsF, presumably via a phenyl-stabilized metalated aziridine [91]. 

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]. 

Table 24 Photo-driven reaction of 2-phenyl-l-azirines with alkoxycarbenes ...

Komendantov et al. found that thermal decomposition of methyl diazoacetate in the presence of benzonitrile yielded two products.<73JOU431> One is the expected 2-phenyl-5-methoxyoxazole 4 in about 35% yield and the other product was methyl 3-phenyl-2//-azirine-2-carboxylate 5 in around 1% yield (Scheme 4). 

Scheme 1 Low-temperature method in the lipase-catalyzed resolution of 3-phenyl-27f-azirine-2-methanol (1) for enhancement of the enantioselectivity.

The lipase-catalyzed resolution of (2/ , 35 )-3-methyl-3-phenyl-2-aziridine-methanol ( )-H by using the low-temperature method gave synthetically useful (2/ ,35 )-ll and its acetate (2S, iR)- a with (25 )-selectivity E = 55 at —40°C), while a similar reaction of (2/ , 3f )-3-methyl-3-phenyl-2-aziridinemethanol ( )-12 gave (25,35 )-12 and its acetate (2/ ,3/ )-12a with (2/ )-selectivity E = 73 at —20°C) (Scheme 2). Compound ( )-ll was prepared conveniently via diastereos-elective addition of MeMgBr to t-butyl 3-phenyl-2//-azirine-2-carboxylate, which was successfully prepared by the Neber reaction of oxime tosylate of t-butyl... 

The first example of a [ 6 + 4] cycloaddition of a nitrile ylid has recently been reported104 irradiation of 3-phenyl-2,2-dimethyl-2i/-azirine (129) in the presence of 6,6-dimethylfulvene (130) in cyclohexane gave the [n6 + 4] adduct 131 together with the [ 4 + 2] adduct 132. 

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