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The nitrone-olefin (3+2) cycloaddition reaction is the combination of a nitrone with an alkene or alkyne to generate an isoxazoline or isoxazolidine via a (3+2) cycloaddition process.〔Confalone, P. N.; Huie, E. M. ''Org. React.'' 1988, ''36'', 1. 〕 This reaction is a 1,3-dipolar cycloaddition, in which the nitrone acts as the 1,3-dipole, and the alkene or alkyne as the dipolarophile. ==Mechanism and stereochemistry== When nitrones are combined with either alkenes or alkynes, (3+2) cycloaddition leads to the formation of a new C–C bond and a new C–O bond. The cycloadditions is stereospecific with respect to the configuration of the alkene; however, diastereoselectivity in reactions of C-substituted nitrones is often low.〔Tufariello, J. J.; Ali, S. A.; Klingele. H. O. ''J. Org. Chem.'' 1979, ''44'', 4213.〕 Regioselectivity is controlled by the dominant frontier orbitals interacting during the reaction, and substrates with electronically distinct substituents tend to react with high regioselectivity. Intramolecular versions of the reaction have been used to synthesize complex polyclic carbon frameworks. Reduction of the N–O linkage leads to 1,3-aminoalcohols. The (3+2) cycloaddition itself is a concerted, pericyclic process whose regiochemistry is controlled by the frontier molecular orbitals on the nitrone (the dipole) and the dipolarophile.〔Houk, K. N. ''J. Am. Chem. Soc.'' 1972, ''94'', 8953.〕 When R' is an electron-donating group, alkyl, or aryl, the dominant FMOs are the HOMO of the dipolarophile and the LUMO of the nitrone. Thus, connecting the atoms whose coefficients in these orbitals are largest, the 5-substituted isoxazolidine is predicted to predominate. On the other hand, when the dipolarophile is electron poor, the HOMOnitrone-LUMOdipolarophile interaction is most important, and the 4-substituted product is favored. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Nitrone-olefin 3+2 cycloaddition」の詳細全文を読む スポンサード リンク
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