"TYC” Reaction between Alkynes and Catechol-Thiol Derivatives Prompted by Metal Nanocatalysis: Mechanism Study by DFT Calculation

CAPURSO, MATÍAS; RADIVOY, GABRIEL; NADOR, FABIANA; DORN, VIVIANA

Congreso; 26th International Electronic Conference on Synthetic Organic Chemistry; 2022

A recently publishedarticle by our research group demonstrated that the hydrothiolation ofactivated alkynes (alkynes with electron-withdrawing groups), “TYC” reaction,is a successful way to functionalize thiols bearing catechols. The reaction waspromoted by a heterogeneous catalyst of copper nanoparticles supported on TiO2(CuNPs/TiO2), showing regio- and stereoselective towards theanti-Markovnikov Z-vinyl sulfide inmost of cases studied, with good to excellent conversions (47-97%). However, noproduct was obtained when a deactivated alkyne such as propynamine was tested,nor with FeNPs/TiO2 catalyst was employed.Through DFT studies, the differentchemical-interactions between the reagents, the metal and the support weremodeled, employing propiolamide and CuNPs/TiO2 as model alkyne andcatalyst respectively. Calculations were made using PBE functional with D3BJdispersion correction, Def2-TZVP basis set and the CPCM model for the solvent(DCM).  DFT studies and experimental datawere consistent with a reaction mechanism based on a copper-catalyzedanti-Markovnikov hydrothiolation process that favors the formation of the Z-vinyl sulfide isomer. On the otherhand, when FeNPs/TiO2 was used to promote the hydrothiolationreaction, no vinyl sulfide was obtained. Theoretical calculation revealed a decreasein charge distribution mainly in the internal C of the triple bond; unlikeCuNPs/TiO2 where the decrease in charge was mainly in the terminal Cand consequently the anti-Markovnikov product was obtained. Besides, the systemwith propynamine revealed that the formation of intermediates in thenucleophilic attack was thermodynamically unfavorable, unlike propiolamide,where the formation of intermediates was mainly exothermic.