We now report the extension of the above studies to the synthesis
of carbamo(dithioperoxo)thioates. Initially, we optimized
the reaction conditions based on the reaction between diethylamine,
carbon disulfide, 2-mercaptoethanol or hexanethiol, and
triethylamine as the base, to investigate the formation of the previously
described lead compounds shown in Fig. 1 (R = n-hexyl,
HOCH2CH2). As a first adaptation of the previously reported
method,8 the use of equimolar quantities of reagents without base
in DMF as the solvent at room temperature gave very low yields of
products. Reactions of equimolar quantities of these reagents promoted
by triethylamine in dichloromethane in the absence of CBr4
did not lead to the desired carbamo(dithioperoxo)thioate products.
Adding one equivalent of CBr4 in dichloromethane produced the
products in 48% and 38% yields, respectively. Surprisingly, the
use of two equivalents of alkyl thiol did not lead to the desired
products, instead yielded the corresponding dithiocarbamates
(confirmed by mass spectrometry and NMR) as by-products.
Finally, it was found that the use of two equivalents of CBr4 gave
the products in good yields (85% and 58%, respectively) under mild
conditions (room temperature, 2 h reaction time). This optimized procedure was subsequently adopted for the synthesis of new carbamo(dithioperoxo)thioate analogues.