Catalytic Regioselective Olefin Hydroarylation(alkenylation) by Sequential Carbonickelation-Hydride Transfer
Chen-Fei Liu1, Xiaohua Luo1,2, Hongyu Wang1
1Department of Chemistry, National University of Singapore, 4 Science Drive 2, Singapore, 117544, Republic of Singapore.
Abstract:
Alkene hydrocarbofunctionalization represents one of the most important classes of chemical transformations, but related branched-selective examples with unactivated olefins are scarce. Here, we report that catalytic amounts of a dimeric Ni(I) complex and an exogenous alkoxide base promote Markovnikov-selective hydroarylation(alkenylation) of unactivated and activated olefins using organo bromides or triflates derived from widely available phenols and ketones. Products bearing aryl- and alkenyl-substituted tertiary and quaternary centers could be isolated in up to 95% yield and >99:1 regioisomeric ratios. Contrary to previous dual-catalytic methods that rely on metal-hydride atom transfer (MHAT) to the olefin prior to carbofunctionalization with a cocatalyst, our mechanistic evidence points toward a nonradical reaction pathway that begins with site-selective carbonickelation across the C═C bond followed by hydride transfer using alkoxide as the hydride source. Utility of the single-catalyst protocol is highlighted through the synthesis of medicinally relevant scaffolds.
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