A DFT Study on the Barton–Kellogg Reaction – The Molecular Mechanism of the Formation of Thiiranes in the Reaction between Diphenyldiazomethane and Diaryl Thioketones

Abstract

The mechanism of the reaction of diphenyldiazomethane with thiobenzophenone and related hetaryl thioketones leading to the corresponding tetrasubstituted thiiranes was studied by means of DFT computational methods at the M06-2X/6-311+G(d) level of theory. The study showed that the initial step of this conversion is a classic one-step (3+2) cycloaddition to give 1,3,4-thiadiazolines in a regioselective manner. These initially formed products undergo a spontaneous extrusion of N2 resulting in the formation of tetraaryl-substituted thiocarbonyl ylides as reactive intermediates. The calculated parameters of the activation for the subsequent 1,3-dipolar electrocyclizations are low (ΔG = 10.8-11.9 kcal/mol) and the only products formed in these reactions are the corresponding thiiranes. The alternative pathways leading to thiocarbonyl ylides via stepwise mechanisms involving zwitterionic or biradical nitrogen-containing intermediates were ruled out.

The Participation of 3,3,3-Trichloro-1-nitroprop-1-ene in the [3 + 2] Cycloaddition Reaction with Selected Nitrile N-Oxides in the Light of the Experimental and MEDT Quantum Chemical Study

“…The Berny method was used in optimizations [69,70]. A similar theory level has been commonly used for the mechanistic research aspects of cycloaddition reactions [71][72][73][74][75] The TSs were characterized through frequency analysis, presenting only one imaginary frequency. The intrinsic reaction coordinate (IRC) paths [76] were computed to find the unique connection between the TSs and the minimum stationary points using the second order González-Schlegel integration method [77,78].…”

A DFT Study on the Molecular Mechanism of Additions of Electrophilic and Nucleophilic Carbenes to Non-Enolizable Cycloaliphatic Thioketones

“…Molecules 2021, 26, x FOR PEER REVIEW 7 of 15 sites. At the same time, the C(1)-C(3) distance remains beyond of the range that is typical for C-C bonds in the transition state [43]. Subsequently, the IRC analysis connects the energetic maximum of TS, with the valleys of individual reagents 1a + 2a and 7aa intermediate.…”

On the Mechanism of the Synthesis of Nitrofunctionalised Δ2-Pyrazolines via [3+2] Cycloaddition Reactions between α-EWG-Activated Nitroethenes and Nitrylimine TAC Systems

“…The regioselectivity of polar processes of non-symmetric reagents can be specified through interaction between the most electrophilic center of the electrophile and the most nucleophilic ones of the nucleophile. For this purpose, electrophilic P k + and nucleophilic P k − Parr functions, derived from the changes of spin electron density reached via the GEDT process from the nucleophile to the electrophile, can be used as a powerful tool in the study of the local reactivity [42][43][44]. According to the nucleophilic P k − Parr functions of nitrylimine components 1a,c,e and the electrophilic P k + Parr functions of nitroethanes 2a-c in order to characterize the most nucleophilic and electrophilic centers of the species involved in this polar 32CA reaction were analyzed (Figure 1).…”