Studies on [PtCl2]‐ or [AuCl]‐Catalyzed Cyclization of 1‐(Indol‐2‐yl)‐2,3‐Allenols: The Effects of Water/Steric Hindrance and 1,2‐Migration Selectivity |
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| Authors: | Youai Qiu Prof. Dr. Chunling Fu Prof. Dr. Xue Zhang Prof. Dr. Shengming Ma |
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| Affiliation: | 1. Laboratory of Molecular Recognition and Synthesis, Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang (P.R. China);2. State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Lu, Shanghai 200032 (P.R. China), Fax: (+86)?21‐626‐093‐05 |
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| Abstract: | The [PtCl2]‐ or [AuCl]‐catalyzed reaction of 1‐(indol‐2‐yl)‐2,3‐allenols occurred smoothly at room temperature to afford a series of poly‐substituted carbazoles efficiently. Compared with the [PtCl2]‐catalyzed process, the [AuCl]‐catalyzed reaction represents a significant advance in terms of the scope and the selectivity. Selective 1,2‐alkyl or aryl migration of the gold carbene intermediate was observed: compared with the methyl group, the isopropyl, cyclopropyl, cyclobutyl, and cyclohexyl groups migrate exclusively; the cyclopropyl group shifts selectively over the ethyl group; the 1,2‐migration of a non‐methyl linear alkyl is faster than methyl group; the phenyl group migrates exclusively over methyl or ethyl group. DFT calculations show that water makes the elimination of H2O facile requiring a much lower energy and validates the migratory preferences of different alkyl or phenyl groups observed. |
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| Keywords: | allenes carbenes density functional calculations gold platinum |
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