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Paper | Special issue | Vol 74, No. 1, 2007, pp.819-825
Published online, 13th November, 2007
DOI: 10.3987/COM-07-S(W)73
Theoretical Studies of 5-exo Selective Intramolecular Cyclization of O-Alkynylbenzoic Acid Catalyzed by Organic Base

Masahiro Terada,* Chikashi Kanazawa, and Masahiro Yamanaka*

*Graduate School of Science, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, sendai 980-8578, Japan


Theoretical studies of the organic base-catalyzed 5-exo intramolecular cyclization of o-alkynylbenzoic acid were documented. The acidic fragment participating in the transition states was shown to reduce the activation energy significantly on the basis of hybrid DFT (BHandHLYP) calculation of 5-exo and 6-endo transition states. Furthermore, preference for the 5-exo cyclization mode was rationalized by natural population analysis of optimized structures of the transition states and the reactants.