Facile construction of symmetric biaryls using (BeDABCO)₂Pd₂Cl₆ as an efficient and highly active catalyst under microwave irradiation

Abstract

An efficient catalytic system using (BeDABCO)2Pd2Cl6 (BeDABCO, benzyl‐1,4‐diazabicyclo[2.2.2]octane) was developed for the homo‐coupling reaction of various aryl halides. Due to the combination of ionic homogeneous metal catalyst and microwave irradiation, symmetric biaryls were produced in excellent yields and short reaction times in N‐methyl‐2‐pyrrolidone at 120 °C. BeDABCO as an efficient ligand and also a quaternary ammonium salt had an efficient stabilizing effect on the Pd(0) species in this coupling reaction. Copyright © 2015 John Wiley & Sons, Ltd.

Oxidative and Reductive Cross-Coupling Reactions Catalyzed by an Anionic “Ligandless” Palladium Complex

“…Among the most straightforward and well-established methods are palladium-catalyzed cross-coupling reactions. − While the Mizoroki–Heck reaction allows access to stilbenes (Scheme a), − the Suzuki–Miyaura reaction, among others, yields biphenyls (Scheme b). − However, most of these cross-coupling reactions suffer from low atom economy and the necessity to use toxic, air-sensitive organometallic reagents. − Among the required aryl halides, aryl chlorides are the reaction partners of choice since they are less expensive, but on the other side, they are also less reactive. One approach to attenuate these drawbacks is the development of the oxidative Heck reaction − of a boronic acid (as a surrogate for the aryl halide) and an alkene for the synthesis of stilbenes (Scheme a). − A viable alternative for the synthesis of symmetric biphenyls is the reductive homodimerization of aryl halides (Scheme b). − …”