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Communication | Regular issue | Vol 45, No. 10, 1997, pp.1873-1878
Published online, 1st January, 1970
DOI: 10.3987/COM-97-7896
1,3-Dipolar Cycloaddition Behavior of Pyrazolone N,N-Dioxides toward Epoxynaphthalene. Effective Secondary N···O Interaction between Addends

Yasuyuki Yoshitake, Masashi Eto, and Kazunobu Harano*

*Faculty of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-hon-machi, Kumamoto 862-0973, Japan

Abstract

Cycloaddition of pyrazolone N,N-dioxides (1) with epoxynaphthalene (2a) gave endo 1,3-dipolar cycloadduct. The origin of the high endo selectivity was explored by MO analysis of the transition structure. Ab initio calculation at several levesl indicates that the orientation complex (OC) forms prior to the formation of the transition state (TS). The interaction between the oxygen of 2a and the nitrogen of the >N→O group of 1 binds two addends together in both OC and TS.