Special Issue Reviews and Accounts ARKIVOC 2009 (i) 129-149
During our work we have unexpectedly found that sulfur monochloride reacted with practically all trialkylamines investigated. But also one of the most interesting finding is that at low temperature for some tertiary amines and at room temperature for 1,4-diazabicyclooctane (DABCO) sulfur monochloride formed reactive complexes.7 Thus, a mixture of equimolar amounts of S2Cl2 and DABCO in chloroform, stored for 1 h at room temperature before use, gave different products to those formed when the heterocycle, S2Cl2 and DABCO were all mixed together at the beginning. We assume that complexes are formed between S2Cl2 and DABCO and we studied their solutions in chloroform by infrared spectroscopy. The S-S absorption band is shifted in the 1:1 mixture from 540 cm-1 to 580 cm-1, and the S – Cl absorption bands of S2Cl2 (• 436 and 452 cm-1) are present in the 1:1 mixture of S2Cl2 and DABCO, but disappear when a second mole of DABCO is added. We assume that the 1:1 mixture contains complex 1 predominantly, and the 1:2 mixture – complex 2 predominantly (Scheme 2).
+ N N + S2Cl2
+ DABCO N NS
N NS + S Cl
SN N _
_
Cl
DABCO 2Cl
complex 1 complex 2
Scheme 2. Complexes of S2Cl2 and DABCO.
More than ten years ago we discovered that N-ethyldiisopropylamine (so called Hünig’s base), having been initially used as an “inert” base, reacted with sulfur monochloride and DABCO by a single step reaction to give an unexpected and novel multisulfur-nitrogen system - tricyclic bis(dithiolo)thiazine dithione 1.8 In this one-pot conversion of Hünig’s base tricycle has been obtained in a one-pot reaction, by mixing two simple commercially available compounds in high yield under mild conditions, to produce a new heterocyclic system by an entirely new method; besides 14 isopropyl C-H bonds were replaced by 10 C-S and two C-C double bonds, while the ethyl group remained intact (Equation 1).
1, 40%
N + S2Cl2 S N S SS S S S (Eq. 1) DABCO ISSN 1551-7012 Page 131 ©ARKAT USA, Inc.
