1, 3-DIPOLAR CYCLOADDITIONS OF AZOMETHINE YLIDE WITH ELECTRON-RICH OR NORMAL OLEFINS

1.氮杂环丙烷中N-取代基对反应的影响研究了分别含有N-苯基或N-苯甲酰基的(α，β-不饱和γ，δ-表亚胺酯1和2)与烯烃的光化学反应和热反应。1与丙烯腈的光反应，以45%的产率得到加合物。另一方面，1和2的热反应和2的光反应没有生成加合物，而是通过C(γ)、O-bong裂解生成烯胺。与氮杂环偶联的N-取代基倾向于裂解氮杂环中的C(γ)、O-bong。侧链上的α取代基对反应的影响研究了α，β-不饱和γ，δ-表亚胺体系在α位和烯烃上具有两个吸电子基团的反应。二腈3和二酯4与丙烯腈的光反应得到了以前得到的加合物。此外，二腈3与异戊二烯和乙酸乙烯酯进行了新型的光环加成反应，丙烯腈加合物的产率随着氮杂环丙烷侧链上电子缺陷的增加而降低。3-位取代氮杂环丙烷的反应为了阐明反应机理，进行了3-甲基和3-苯基取代氮杂环丙烷5和6与烯烃的反应。5的光化学反应和热反应表明，氮杂环丙烷的开环反应和与烯烃的环加成反应并不协调进行。另一方面，在光化学反应和热反应中，氮杂环丙烷6发生了开环和环加成反应，生成了加合物。3-对氰基苯基(更缺乏电子的取代基)氮杂环丙烷与异戊二烯和乙酸乙烯酯不反应，氮杂环丙烷5和6与分子氧光化学反应生成二恶唑烷及其分解产物。结果表明，该反应中间体具有双自由基性质。

1. Effects of the N-Substituent in Aziridine on the ReactionThe photochemical and thermal reactions of (α, β-unsaturated γ, δ-epimino esters 1 and 2 possessing respectively N-phenyl or N-benzoyl group and olefins were studied. The photoreaction of 1 with acrylonitrile gave the adduct in 45% yield. On the other hand, the thermal reactions of 1 and 2 and the photoreactions of 2 afforded no adduct, but enamines formed via C(γ), O-bong cleavage. The N-substituents conjugated with the aziridine ring tend to cleave the C(γ), O-bong in aziridine.2. Effects of the α-Substituent in the side chain on the ReactionThe reactions of α, β-unsaturated γ, δ-epimino system possessing two electron withdrawing groups in α-position and olefins were investigated. The photoreactions of the dinitrile 3 and the diester 4 and acrylonitrile gave the adducts as obtained before. Furthermore, the novel photocycloadditions of the dinitrile 3 proceeded with isoprene and vinyl acetate successfully.The yields of the acrylonitrile adducts decreased with increasing the electron deficiency in the side chain of aziridine.3. Reactions of Aziridines Possessing Substituent at 3-PositionIn order to clarify the reaction mechanism, the reactions of 3-methyl and 3-phenyl substituted aziridines 5 and 6 and olefins were performed. The photochemical and thermal reaction of 5 shows that the ring-opening of aziridine and cycloaddition with olefins did not proceed concertedly. On the other hand, on the photochemical and thermal reactions the aziridine 6 underwent ring-opening and cycloaddition concertedly leading to adducts. The 3-p-cyanophenyl (more electron deficient substituent) aziridine did not react with isoprene and vinyl acetate.The aziridines 5 and 6 react with molecular oxygen photochemically affording the dioxazolidine and its decomposed compounds. The results may suggest that the reaction intermediate possesses biradical character.