Abstract
Since the landmark work of Heck, Negishi and Suzuki on Pd-catalyzed crossing coupling reactions, innovative discovery of new reactions forming C-C bonds and constructing functional olefins via nonmetal catalysts remains an imperative area in organic chemistry. Herein, we report a transition-metal-free arylation method of vinyl pinacolboronates with diaryliodonium salts to form C(sp2)-C(sp2) bond and provide trans-arylvinylboronates. The resulting vinylboronates can further react with the remaining aryl iodides (generated from diaryliodonium salts) via Suzuki coupling to afford functional olefins, offering an efficient use of aryliodonium salts. Computational mechanistic studies suggest radical-pair pathway of the diaryliodonium salts promoted by the multi-functional wet carbonate.
Highlights
Since the landmark work of Heck, Negishi and Suzuki on Pd-catalyzed crossing coupling reactions, innovative discovery of new reactions forming C-C bonds and constructing functional olefins via nonmetal catalysts remains an imperative area in organic chemistry
Our new findings disclose the radical arylation of vinyl pinacolborate 2 can be realized with diaryliodonium salts (Ar1I+Ar2OTf−) 1 promoted by wet base, so it is characterized by the simplicity and the possibility of further functionalization (Fig. 1c)
On the basis of our group’s previous research on diaryliodonium salts[30,31,32,33,34], here we report a tandom process in which an aryl iodide generated in situ is captured in a second step by a Suzuki reaction, yielding aryl olefins
Summary
84(82)e aUnless noted, reactions were performed with 1a (0.15 mmol), 2a (2.0 eq.), catalyst (10 mol%), and additive (40 eq.), in solvent (1 mL) at the temperature described. bDetermined by GC analysis using n-dodecane as an internal standard. c2.0 equiv. of TBAF was used. dE/Z isomer of 3a was 2/1. eIsolated yield. fNo product. 84(82)e aUnless noted, reactions were performed with 1a (0.15 mmol), 2a (2.0 eq.), catalyst (10 mol%), and additive (40 eq.), in solvent (1 mL) at the temperature described. BDetermined by GC analysis using n-dodecane as an internal standard. Iterative synthesis of aryl olefins using alkenyl boronic esters as intermediates (Fig. 1c). Of note, it will be a novel approach for the iterative synthesis of aryl olefins using alkenyl boronic esters as intermediate
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