Alkene Isomerization–Hydroarylation Tandem Catalysis: Indole C2‐Alkylation with Aryl‐Substituted Alkenes Leading to 1,1‐Diarylalkanes |
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Authors: | Takeshi Yamakawa Prof Naohiko Yoshikai |
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Institution: | Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore, Fax: (+65) 6791‐1961 |
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Abstract: | A cobalt‐N‐heterocyclic carbene catalyst generated from CoBr2, imidazolium salt, and cyclohexylmagnesium bromide was found to promote the imine‐directed C2‐alkylation of indoles with nonconjugated arylalkenes through a tandem alkene isomerization–hydroarylation process, affording 1,1‐diarylalkanes with exclusive regioselectivity. The feasibility of the tandem catalysis was demonstrated for allyl‐, homoallyl‐, and bishomoallylbenzene derivatives. The catalytic system is also applicable to a variety of β‐substituted styrene derivatives. Mechanistic experiments using deuterium‐labeled indole substrate and Grignard reagent provided insight into the cobalt‐mediated C? H activation step, which likely involves exchange of the C2‐hydrogen atom of the former and the β‐hydrogen atoms of the latter. |
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Keywords: | alkenes alkylation C H functionalization cobalt indoles |
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