ChemInform Abstract: SYNTHESIS OF TOSYLAMIDINES FROM THIOAMIDES

Reactions of Thioacetamide Derivatives with Sulfonyl Azides: An Approach to Active‐Methylene N‐Sulfonylacetamidines

“…Thioamide 8a was found to be unreactive when we used ethanol at room temperature, under the conditions of Aswad 17. We also found that the reaction of thioamide 8a with tosyl azide in pyridine, according to Zelenskaya et al,18 led to an oily brown residue containing traces of cyanoacetamidine 10a . All our attempts to improve this protocol failed.…”

“…Two papers, apart from ours,17 have been published on the reactions of thioamides with sulfonyl azides. The first report, from O. V. Zelenskaya et al, deals with the preparation of sulfonyl amidines by the reaction of thioamides with tosyl azide under relatively harsh conditions: heating at 90–100 °C in pyridine for 5 h 18. Conversely, M. Aswad et al found that thioamides of acetic and benzoic acids 3 and cyclic thioamides react with benzenesulfonyl and mesyl azides under very mild conditions in ethanol or other organic solvents, or even in water, under catalyst‐free conditions, to form the corresponding amidines (i.e., 4 ) in very good yields 16.…”

“…Conversely, M. Aswad et al found that thioamides of acetic and benzoic acids 3 and cyclic thioamides react with benzenesulfonyl and mesyl azides under very mild conditions in ethanol or other organic solvents, or even in water, under catalyst‐free conditions, to form the corresponding amidines (i.e., 4 ) in very good yields 16. Based on literature data on the reaction of thioamides with azides,14–18 apart from amidines, various heterocyclic compounds could be formed as a result of the reactions of malonic acid thioamides and 2‐arylthioacetamides 8 with sulfonyl azides 9 (Figure 1). This complicates the development of a selective and efficient method for a base‐catalyzed preparation of N ‐sulfonylacetamidines of type 10 .…”

Coupling reaction of thioamides with sulfonyl azides: an efficient catalyst-free click-type ligation under mild conditions

“…Previous work by O. V. Zelenskaya provides encouraging precedent. 5 In their report, however, thioamides were examined under rather harsh conditions: heating at 90-100 1C in pyridine for up to 5 h. Here we show that such harsh conditions are not necessary. Thioamides and sulfonyl azides undergo an efficient coupling reaction under mild and catalyst-free conditions, providing a versatile means of achieving click-type ligations of aliphatic and aromatic substrates in a range of solvents (Scheme 1).…”