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DFT study on Ru II ‐catalyzed cyclization of terminal alkynals to cycloalkenes
Author(s) -
Zhang Jinsheng,
Shen Wei,
Liu Ruiqiu,
Yu Youqing,
Wu Hailing,
Li Ming
Publication year - 2008
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.21861
Subject(s) - chemistry , carbene , electrophile , nucleophile , ruthenium , medicinal chemistry , alkyne , catalysis , triple bond , photochemistry , allylic rearrangement , natural bond orbital , cationic polymerization , density functional theory , computational chemistry , double bond , polymer chemistry , organic chemistry
The reaction mechanism of [CpRu(MeCN) 3 ]PF 6 ‐catalyzed cyclization of terminal alkynals 1 to cycloalkenes 2 was investigated by means of density functional methods combined with polarizable continuum models. Calculations indicate that the coordination of the cationic catalyst [CpRu(CH 3 CN) 2 ] + to the carbon–carbon triple bond of the substrate 1 enhances the electrophilicity of alkynyl group, and the subsequent nucleophilic attack of the carbonyl oxygen to the electron‐deficient alkyne forms ate complex IM2 , which would further isomerize into 2H‐oxete complex IM3 . Then a replacement of MeCN by AcOH occurs, followed by two proton‐migrations, which leads to a Fischer‐type carbene complex IM6 . Finally, a decarbonylation takes place leading to cycloalkene 2 . The terminal alkynal is activated by its combination with ruthenium, which leads to a decrease in the natural bond orbital energy of π* (C1C2) . The four‐membered ring formation is the rate‐controlling step. However, AcOH helps proton shift through coordination with metal center and decreases the reaction energy barriers. Throughout the reactions, all the Ru II complexes obey the 18‐electron‐rule. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009