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Ligand effect of bulky 2,2-dialkyl-1-phosphaethenes on Au-catalyzed cycloisomerization of 1,6-enynes and lactonization of pent-4-ynoic acids |
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| Authors: | Shigekazu Ito Shuhei Kusano Koichi Mikami |
| Institution: | a Department of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, Ookayama, Meguro, Tokyo 152-8552, Japan b Department of Chemistry, Graduate School of Science, Tohoku University, Aoba, Sendai 980-8578, Japan c Department of Chemistry, The University of Alabama, Tuscaloosa, AL 35487-0336, USA |
| Abstract: | 2,2-Dimethyl- and 2-benzyl-2-methyl-1-(2,4,6-tri-tert-butylphenyl)-1-phosphaethenes were employed as ligand of mononuclear chlorogold(I) complexes, which catalyzed cycloisomerization of 1,6-enyne affording vinylcyclopentene exclusively in the absence of silver co-catalyst. The reaction mechanisms are discussed based on DFT calculations. In addition to the cycloisomerization, the phosphaalkene-chlorogold(I) complexes catalyzed cyclization of pent-4-ynoic acids providing γ-methylene-γ-lactones under basic conditions. |
| Keywords: | Phosphaalkenes Gold catalysts Enyne cyclization Steric protection γ-Lactones |
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