Herein, a donor/acceptor‐free carbene insertion reaction of an S–S bond through a radical process is presented. This catalyst‐free reaction was thermally induced and provided the dithioketal products in moderate to high yields. A mechanism involving radical intermediates was proposed according to the computational study, and these intermediates were verified experimentally and intercepted for the first time by using a cross‐coupling reaction.

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Computational studies were carried out to investigate the detailed mechanism of Pd(0) and benzoic acid co-catalyzed hydroamination of internal alkynes. In the presence of the benzoic acid, the formation of a hydridopalladium intermediate via the oxidative addition (OA) of the O-H bond of benzoic acid into the Pd(0) complex center might not be a favorable reaction pathway to start the reaction. Instead, after the coordination of benzoic acid with the Pd(0)-alkyne complex, a proton transfer process from the acid to carbon of alkyne is found to be a favorable pathway, leading to the alkenyl(PhCOO)Pd(II) intermediate. Next, the resulting alkenyl(PhCOO)Pd(II) species would produce phenylallene intermediate via a β-H elimination step assisted by the formed benzoate anion. Subsequently, the benzoic acid might undergo a second proton step to the phenylallene intermediate to produce the π-allylpalladium species. Finally, the amine substrate could undergo a nucleophilic addition to the terminal carbon of the π-allylpalladium species to produce the hydroamination product.