Azirines 2-allyl substituted

As unusual aspect of the intramolecular photocyclization of 2-allyl-substituted 2/f-azirines was uncovered during a study of the photochemistry of -2-(2-butenyl)-2-methyl-3-phenyl-2H-azirine (185). Irradiation of 185 in cyclohexane gave rise to one major product (>95%) which was identified as nrfo-3,6-dimethyl-l-phenyl-2-azabicyclo[3.1.0]hex-2-ene (186). The formation... 

Several additional examples in the literature demonstrate the generality of the 1,1 trapping of nitrile ylides. Thus treatment of o-allyl-substituted imidoyl chloride 194 with triethylamine gave benzobicyclo[3.1.0]hex-2-ene 196. Irradiation of the closely related methyl-substituted azirine system 197 produced a mixture of endo- and ex o-benzobicyclohexenes 199 in quantitative yield.No detectable quantities of the isomeric 1,3-dipolar adduct were observed in either system. In the case of 197, the major product (exo-199) is the thermodynamically more favored exo isomer. 

One of the best known reactions of 1-azirines is the acid/catalyzed hydrolysis to aminoketones. Since the Neber reaction also accomplishes this same synthetic end, this reaction may appear to have little practical value. This is not the situation because with the Neber reaction there is no control over the aminoketone that will be obtained from a given ketone. For example, when oxime (127) derived from benzyl methyl ketone (126) is subjected to the Neber reaction aminoketone 128 is obtained.59 The amino function is substituted for the most acidic a-hydrogen. The isomeric aminoketone (132) that could not be prepared by the Neber reaction can be formed by the hydrolysis of 1-azirine (131). The synthesis of this 1-azirine has been accomplished from allyl benzene (129) through vinyl azide (130) using iodine azide.22... 

Ohler. E.. and Kanzler, S., (2//-A/.irin-2-yl)mcthy I Iphosphonates. Synthesis from allylic a- and y-hydroxyphosphonates and application to diastereoselective formation of substituted [(azirin-2-yl)methyl]phosphonates, Liebigs Ann. Chem., 867, 1994. 

As was mentioned in the previous section, the HOMO and second LUMO of the bent nitrile ylide bear a strong resemblance to the HOMO and LUMO of a singlet carbene. Since carbenes are known to react readily with double bonds, a 1,1-cycloaddition reaction of nitrile ylides can be expected. Padwa and Carlsen uncovered the first example of such a process during an investigation of the photochemistry of a number of 2-ally 1-substituted 2ff-azirines. When a thoroughly deaerated solution of 2-allyl-2-methyl-3-phenyl-2/f-azirine (177) was irradiated in cyclohexane with light of wavelength >280 nm for 15 min, an extremely rapid and clean conversion to 3-methyl-l-phenyl-2-azabicyclo[3.1.0]hex-2-ene (179) was observed. When the irradiation of 177 was carried out to 20% conversion, however, a 1 1 mixture of 179 and 1-methyl-3-phenyl-2-azabicyclo[3.1.0]hex-2-ene (178) was quantitatively isomer-ized to 179. The photochemical behavior of the isomeric 2-allyl-3-methyl-2-phenyl-2if-azirine (180) afforded a quantitative yield of azabicyclohexene (179). A control experiment showed that 177 and 180 were not interconverted by a... 

Thermolysis of 2-allyl-3-methyl-2-phenyl-substituted 2/f-azirines has been found to afford mixtures of azabicyclohexenes (395) and indoles (396). The distribution of products with this ring system is controlled by the rates of nitrene attack on the double bond vs. electrocyclization on the adjacent phenyl ring. 

The thermal behavior of the carbomethoxy-substituted allyl 2/f-azirine 400... 

Protonation of CpMo(C0)2(Tl -allyl) with HBF generates CpMo(CO) (n -propene)FBF, from which both olefin and anion can be displaced by PPh to give [CpMo(CO)2(PPh )2 Reaction of Cp2M02(CO) with 2-substituted azirines gives CpMo(C0)2 (ri -HN-CR-CH2) (R=>Ph, p-tolyl) which rearrange in solution via a... 

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