Efficient synthesis of sulfonic, phosphoric, and phosphinic esters employing alkylating polymer-bound reagents

The efficient esterification of various sulfonic acids and sulfonates using polymer-bound triazenes based on the triazene T2* linker is described. Esterification of enantiopure alpha-substituted sodium sulfonates was performed in the presence of an alkylating resin without racemization. Racemization is a serious drawback in the esterification route via sulfonyl chlorides because of intermediate sulfene formation. To demonstrate the versatility of this protocol, phosphoric and phosphinic acids have been converted into the corresponding esters as well. All products were obtained in good yield and excellent purities without any further purification steps.