Cycloadditions and Methylene Transfer in Reactions of Substituted Thiocarbonyl S-Methylides with Thiobenzophenone: A Computational Study

✍ Scribed by Reiner Sustmann; Willi Sicking; Rolf Huisgen

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 259 KB
• Volume: 2005
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/ejoc.200400764

✦ Synopsis

Abstract

Regiochemistry and methylene transfer reactions in cycloadditions of aliphatic thiocarbonyl S‐methylides and thiobenzophenone are analyzed by ab initio [(U)HF/3‐21G*] and DFT calculations [(U)B3LYP/6‐31G*//(U)HF/3‐21G* and (U)B3LYP/6‐31G*]. The formation of regioisomeric 1,3‐dithiolanes is explained by the competition of concerted (2,4‐substituted 1,3‐dithiolane) and stepwise cycloaddition via C,C‐biradicals (4,5‐substituted 1,3‐dithiolane). Aliphatic thiocarbonyl S‐methylides with sterically demanding substituents undergo substantial methylene transfer in the reaction with thiobenzophenone. This process involves dissociation of the C,C‐biradical intermediate with liberation of thiobenzophenone S‐methylide which, in turn, combines with a second molecule of thiobenzophenone. Calculated activation parameters for the different processes are in agreement with the experimental observations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)