Synthesis of Sulfonic Acid Salts and Sulfonic Acids by Advanced Cross‐Coupling Reaction of Vinyl Sulfonates

The present work describes an advanced cross‐coupling reaction of vinyl sulfonates for the synthesis of sulfonic acid salts and sulfonic acids under mild reaction conditions. The regioselectivity of the double Negishi reaction was achieved by means of the different reactivity of the C−Br and activated C−O bonds. The cross‐coupling reaction leads to a mixture of alkenes and sulfonic acid salts. The separation of alkenes and sulfonic acid salts is achieved through the low solubility of sulfonic acid sodium salts after workup. In addition, the developed procedure is also used for the atom‐economical preparation of cyclooxygenase‐2 inhibitors (COX‐2). The preparation of sulfonic acids and sulfonic acid salts by the Negishi reaction of vinyl sulfonates is described. The cross‐coupling reaction benefits from easy separation of the formed alkenes and sulfonic acid salts on the basis of their different solubility in organic solvents.