期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 17, 期 36, 页码 10081-10088出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201101363
关键词
alcohols; cyclization; gold; homogeneous catalysis; nitrogen heterocycles
资金
- University Research Committee [RG55/06]
- Nanyang Technological University (NTU)
- Science and Engineering Research Council [092 101 0053]
- A*STAR, Singapore
A synthetic method that relies on gold-catalysed cyclopropyl carbinol rearrangement of 2-tosylaminophenyl cyclopropylmethanols to prepare 2,3-dihydro-1H-benzo[b]azepines and 2-vinylindolines efficiently is reported. The reactions were shown to be chemoselective, with secondary and tertiary alcohol substrates exclusively providing benzo-fused five- and seven-membered ring products, respectively. The ring-forming process was also found to proceed in moderate to excellent yields under mild conditions only in the presence of the gold and silver catalyst combination. The mechanism is thought to involve activation of the alcohol by the (p-CF3C6H4)(3)PAuCl/AgOTf (Tf = triflate) catalyst, resulting in ionization of the starting material. The tertiary carbocationic intermediate generated in situ in this manner then triggers ring-opening of the cyclopropane moiety and trapping by the tethered aniline group to give the 2,3-dihydro-1H-benzo[b]azepine. Cyclopropane ring fragmentation of the secondary carbocationic analogue, on the other hand, results in diene formation followed by subsequent intramolecular hydroamination to afford the 2-vinylindoline.
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