Computational insights into the S₃transfer reaction: A special case of double group transfer reaction featuring bicyclically delocalized aromatic transition state geometries

Abstract

An unusual pericyclic process that involves the intermolecular transfer of thiozone (S ) is computationally described. The process can be considered as a special case of double group transfer reaction whereby the two migrating groups are connected to the same substituent, taking place in a concerted manner via transition states featuring two five-membered C S rings fused together. Analysis of the aromaticity at the TS geometries by computing NICS values at the (3,+1) RCPS as well as ACID calculations confirms the aromatic character of each C S ring, thus resulting in bicyclically delocalized aromatic structures. The free energy barriers for the transfer of S are relatively similar (40-50 kcal mol ) to those computed for typical double H group transfer reactions. The similarities and differences between these processes have been further analysed by applying ASM-EDA and NBO approaches to the model reactions between ethene and ethane, and ethene and 1,2,3-trithiolane. © 2017 Wiley Periodicals, Inc.

The application of aromaticity and antiaromaticity to reaction mechanisms

“…Interestingly, Algarra reported an unusual pericyclic reaction that involves an intermolecular S 3 transfer ( Fig. 4 h), which occurs via a concerted transition state featuring two five-membered C 2 S 3 fused rings [65] . The calculated NICS at the (3,+1) ring critical points of electron density and ACID suggest that the two five-membered C 2 S 3 rings are aromatic.…”