New publication in RSC Advances entitled “Thiol-yne click reaction: an interesting way to derive thiol-provided catechols” as a collaboration with Dr. Fabiana Nador and Dr. Juan Mancebo-Aracil from Instituto de Química del Sur (INQUISUR-CONICET, Universidad Nacional del Sur, Bahía Blanca, Argentina).
In this work, the authors attempted to apply thiol-yne click (TYC) reaction to the modification of catechol structures bearing a thiol functionality as end-group. In most cases, the addition of a base to promote the hydrothiolation reaction of activated alkynes is mandatory. However, the catechol moiety is not compatible with even moderately basic media due to its oxidation to o-quinone by atmospheric oxygen or another mild oxidant. An alternative is to carry out the hydrothiolation of alkynes substituted with electron-withdrawing groups and promoted by transition metals, thus taking advantage of the beneficial effect of an increase in the nucleophilicity of the thiol caused by the presence of metal species. In this context, copper-based catalytic systems are of particular interest since the activation of both the alkyne and the thiol is thought to be the key step in this reaction.
ABSTRACT: The hydrothiolation of activated alkynes is presented as an attractive and powerful way to functionalize thiols bearing catechols. The reaction was promoted by a heterogeneous catalyst composed of copper nanoparticles supported on TiO2 (CuNPs/TiO2) in 1,2-dichloroethane (1,2-DCE) under heating at 80 °C. The catalyst could be recovered and reused in three consecutive cycles, showing a slight decrease in its catalytic activity. Thiol derivatives bearing catechol moieties, obtained through a versatile Michael addition, were reacted with different activated alkynes, such as methyl propiolate, propiolic acid, propiolamide or 2-ethynylpyridine. The reaction was shown to be regio- and stereoselective towards anti-Markovnikov Z-vinyl sulfide in most cases studied. Finally, some catechol derivatives obtained were tested as ligands in the preparation of coordination polymer nanoparticles (CNPs), by taking the advantage of their different coordination sites with metals such as iron and cobalt.