Suzuki electron-poor arylboronic acids

One of the challenges in the Suzuki-type cross-coupling is to extend this reaction from electron-rich aryl iodides, bromides, and triflates to less reactive aryl sulfonates and aryl chlorides, which show poor reactivity in terms of oxidative addition in the catalytic cycle. Aryl mesylates, benzenesulfonates, and tosylates are much less expensive than triflates, and are unreactive toward palladium catalysts. The Ni(0)-catalyzed Suzuki-type cross-coupling reaction of aryl sulfonates, including mesylates, with arylboronic acids in the presence of K3P04 has been reported [123]. 

Upon investigating the literature, Lauren noted that arylboronic acids substituted with electron-withdrawing groups often experience extensive protodeboronation and poor yields under the standard Suzuki conditions that utilize aqueous NaaCOs as a base. A solution to this problem lies in either the use of a milder base or nonaqueous conditions. Therefore, Lauren chose to employ NaHCOj as a base. The arylboronic acid derivative of 6-bromopiperonal was coupled with the suitably elaborated aryl iodide to provide the desired biaryl ( )-3 in moderate yields (Eq. 15). 

---