The mechanisms for triple gold(I)-catalyzed (4+1) cycloaddition of methylenecyclopropane with 7-naphthyl-1,3,5-cycloheptatriene: Insight into from density functional calculations

The mechanisms of (4+1) cycloaddition for the reaction of 7-naphthyl-1,3,5-cycloheptatriene with methylenecyclopropane via triple gold(I) catalysis to generate cyclopentene have been studied by density functional theory (OFT) calculations. Free energy profiles have been calculated for the Au-, Cu- and Ag-catalyzed reactions to evaluate possibility of these cycloaddition reactions. The calculations showed that the reaction mechanism proceeds through the transformation of methylenecyclopropane to afford cyclobutene via an isomerisation, and subsequent retro-Buchner reaction takes place to give the gold(I) carbene. Finally, cyclopentene is produced catalyzed by carbene complex. On the basis of the calculations, two C-C bonds cleavage in retro-Buchner reaction was predicted to be the rate-limiting step with a free energy barrier of 27.1 kcal/mol. We also demonstrate why no reaction occurs for the other Ag, Cu and Au catalysts studied. Present calculations are consistent with the experimental observations and could provide new insights into the gold catalysis. (C) 2016 Elsevier B.V. All rights reserved.