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Addition of Sulfonic Acids to Terminal Alkynes Catalyzed by a Rhodium Complex: Ligand Concentration‐Controlled Reaction Selectivity
Author(s) -
Yang Yong,
Moschetta Eric G.,
Rioux Robert M.
Publication year - 2013
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201300228
Subject(s) - chemistry , sulfonate , regioselectivity , catalysis , markovnikov's rule , ligand (biochemistry) , rhodium , sulfonic acid , salt (chemistry) , medicinal chemistry , organic chemistry , selectivity , sodium , biochemistry , receptor
A Rh‐catalyzed process for the regioselective formation of vinyl sulfonate esters in moderate to high yields through the hydrosulfonation of alkynes with sulfonic acids has been developed. Our synthetic approach is capable of adding a variety of alkynes to a set of sulfonic acids and is amenable to different phosphorus ligands, solvents, and Rh precursors. We control the chemo‐ and regioselectivity of the reaction to the Markovnikov vinyl sulfonate ester by tuning the concentration of the exogenous ligand, PPh 3 , which forms the active RhP species in situ. At lower PPh 3 concentrations, the reaction favors the formation of vinyl sulfonate esters, whereas at higher PPh 3 concentrations, the reaction favors the formation of vinylphosphonium salts. We perform Hammett analyses and kinetic isotope effect experiments to determine the steps of the catalytic mechanism. Reaction data for substituted acetylenes indicates syn and anti addition occur across the triple bond. Experiments performed with the vinylphosphonium salt as the exogenous ligand determined that the formation of the salt was not a necessary step in the catalytic mechanism for the direct formation of the vinyl sulfonate esters.