α-Phosphonovinyl Arylsulfonates: An Attractive Partner for the Synthesis of α-Substituted Vinylphosphonates through Palladium-Catalyzed Suzuki Reactions

It has been demonstrated that a variety of alpha-phosphonovinyl arylsulfonates with electron-neutral, -donating, and -withdrawing groups on the phenyl ring could be conveniently and efficiently prepared. In the presence of a Pd(OAc)(2)/SPhos-based catalyst, various organoboron compounds could be employed as the nucleophilic coupling partners, such as organoboronic acids, boronate esters, and organotrifluoroborates. The newly developed O-centered electrophiles could couple with a multitude of aryl, heteroaryl, and alkylboron reagents, to give alpha-substituted vinylphosphonates in moderate to excellent yields. Generally, the Suzuki reaction is tolerant of extensive substitution at the aromatic ring of both electrophilic and nucleophilic coupling partners. As in the case of the Suzuki reaction of 8-quinolineboronic acid, proper choice of a-phosphonovinyl arylsulfonates is critical to efficient coupling. Moreover, the prospect for application of this method to complex synthesis has been demonstrated through the coupling of estrone-derived arylborons. The present protocol also features mild conditions and high efficiency.