Generation and selected reactions of chlorinated thiocarbonyl S-imides

A DFT study on the mechanism of the formation of 1,4,2,3‐dithiadiazinanes by head‐to‐head [3 + 3] cyclodimerization of thiocarbonylS‐imides

“…Obviously, the calculated data agree well with the X‐ray data observed for the final product 2c. [ 10 ] Suitable X‐ray data of a stable, crystalline thiocarbonyl S ‐imide are not available. To the best of our knowledge, only one publication on the X‐ray structure of a thiocarbonyl S ‐imide exists in the literature.…”

“…In continuation of our formerly published semiempirical PM7 [ 18 ] results concerning the observed formation of 5,5,6,6‐tetrachloro‐1,4,2,3‐dithiadiazinanes 2 instead of the expected 3,3,6,6‐tetrachloro‐1,4,2,5‐dithiadiazinanes 3 , [ 9,10 ] we now conducted more sophisticated DFT calculations on the reaction mechanism.…”

“…This dimerization could occur either as a head‐to‐head ( → 1,4,2,3‐dithiadiazinane) or as a head‐to‐tail ( → 1,4,2,5‐dithiadiazinane) process. [ 9,10 ]…”

“…Interestingly and in contrast to the expected head‐to‐tail 33CD, preferably the regioselective head‐to‐head 33CD to form the corresponding 1,4,2,3‐dithiadiazinanes 2 (R 1 = Cl, R 2 = Ar) occurs with thiophosgene S ‐( N ‐aryl)imides 1 (R 1 = Cl, R 2 = Ar). [ 9,10 ] This reaction course is typical of the 33CD reaction of another type of sulfur‐centered TACs, the better known thiocarbonyl S ‐methanides Ar 2 C=S=CR 2 , which leads to 4,4,5,5‐tetraaryl‐1,4‐dithianes. [ 11,12 ] The aim of our computational study was thus to propose an explanation of this counter‐intuitive regioselectivity.…”

“…[ 1,2 ] Their structures have been identified by NMR spectroscopy and X‐ray diffraction analyses. [ 10 ] We focused our theoretical investigations, which we present here, on 2a–c and 3a–c and on the mechanism that controls the chemoselective formation of the conceivable isomers 2 or 3 .…”