Efficient Synthesis of Sulfonic, Phosphoric, and Phosphinic Esters Employing Alkylating Polymer-Bound Reagents

Abstract

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.

The Virtue of the Multifunctional Triazene Linkers in the Efficient Solid-Phase Synthesis of Heterocycle Libraries

“…The newly formed diazonium ion undergoes substitution with the nucleophile present in the reaction mixture. Therefore, alkyl halides 103-X , alcohols 103-OH , and ethers 103-OR 1 , as well as alkyl carboxylic esters 103-OCOR , sulfonic esters 103-OSO 2 R , phosphoric esters 103-OPO(OR) 2 , and phosphinic esters 103-OPO(H)(OR) , could be formed by cleavage with trimethylsilyl halides (X = I, Br, Cl), aqueous trifluoroacetic acid, carboxylic acids, sulfonic acids, phosphoric acids, and phosphinic acids, respectively. The regioselectivity of the cleavage can be explained by the presence of one tautomer of the triazene in which the hydrogen atom is on the triazene nitrogen, which is linked to the arene ring.…”

Solid-Supported Reagents and Catch-and-Release Techniques in Organic Synthesis

“…Different alkylating triazenes were prepared, and resulted in the production of the corresponding alkyl sulfonates and phosphonates in good yields and purity. 107 Using the same method, enantioenriched R-substituted sodium sulfonates, synthesised via asymmetric synthesis, were transformed into esters without loss of enantiomeric excess. Polymer-supported methyl sulfonate 271 was prepared by the reaction of polymer-supported sulfonic acid with trimethyl orthoacetate, in the absence of solvent, at room temperature.…”

The Structural Influence in the Stability of Polymer‐Bound Diazonium Salts

“…[32] We have synthesized diazonium ions with different substitution pattern and used them for the synthesis of triazenes. [33][34][35][36] Rademann et al used the T2-para resin for the synthesis of triazenes, [37] while Struber et al developed solidphase bound triazenes, based on nitration and further functionalization of polystyrene, and investigated their chemical and thermophysical properties. [38] There is, however, less knowledge on the stability of diazonium ions on solid supports.…”