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.

Reduction of the PdPEPPSI precatalyst to a Pd⁰ species is generally thought to be essential to drive Buchwald–Hartwig amination reactions through the well- documented Pd⁰/Pd^II catalytic cycle and little attention has been paid to other possible mechanisms. Considered here is the PdPEPPSI-catalyzed aryl amination of chlorobenzene with aniline. A neat reaction system was used in new experiments, from which the potentially reductive roles of the solvent and labile ligand of the PEPPSI complex in leading to Pd⁰ species are ruled out. Computational results demonstrate that anilido-containing Pd^II intermediates involving σ-bond metathesis in pathways leading to the diphenylamine product have relatively low barriers. Such pathways are more favorable energetically than the corresponding reductive elimination reactions resulting in Pd⁰ species and other putative routes, such as the Pd^II/Pd^IV mechanism, single electron transfer mechanism, and halide atom transfer mechanism. In some special cases, if reactants/additives are inadequate to reduce a Pd^II precatalyst, a Pd^II-involved σ-bond metathesis mechanism might be feasible to drive the Buchwald–Hartwig amination reactions.

A new reactivity pattern of α-aminoalkyl radicals, involving nucleophilic attack on CN triple bonds under thermal conditions, has been developed to construct α-amino nitriles. In contrast to previous CH functionalization of tertiary amines involving α-aminoalkyl radicals, this methodology does not require the use of photocatalytic conditions or a transition-metal catalyst. Inexpensive and nontoxic phenylacetonitrile was chosen as cyano source for this α-aminonitrile forming reaction. A plausible mechanism is proposed based upon experimental and computational results. An α-aminoalkyl radical intermediate and benzoyl cyanide have been shown to be key intermediates in this green and mild radical process. Nucleophilic attack of the α-aminoalkyl radical on the CN bond of PhCOCN followed by an elimination step forms the desired α-aminonitrile and an acyl radical.

Cyclobutane-1,2,3,4-tetraone, (CO)₄, was computationally predicted and, subsequently, experimentally confirmed to have a triplet ground state, in which a b_2g σ MO and an a_2u π MO were each singly occupied. In contrast, the (U)CCSD(T) calculations reported herein found that cyclobutane-1,2,3,4-tetrathione, (CS)₄, and cyclobutane-1,2,3,4-tetraselenone, (CSe)₄, both had singlet ground states, in which the b_2g σ MO was doubly occupied and the a_2u π MO was empty. Our calculations showed that both the longer CX distances and smaller coefficients on the carbon atoms in the b_2g and a_2u MOs of (CS)₄ and (CSe)₄ contributed to the difference between the ground states of these two molecules and the ground state of (CO)₄. An experimental test of the prediction of a singlet ground state for (CS)₄ is proposed.