Novel conversion of 6H‐1,3,5‐oxathiazine S‐oxides into 5‐membered heterocyclic compounds

Abstract

5H-1,2,4-oxathiazoles were efficiently synthesized from 6 H-1,3,5-oxathiazine S-oxides by thermal cycloreversion of the substrates and the products were effectively converted into 1,2,4-thiadiazoles.

An unexpected synthesis of 3,5-diaryl-1,2,4-thiadiazoles from thiobenzamides and methyl bromocyanoacetate

“…11 Other more complicated methods are also reported: from the corresponding oxathiazolone, 12 benzenecarboximidamide and diethyl azodicarboxylate, 13 or from 1,2,4-oxathiazoles and Lewis acid. 14 Thermal cycloreversion of 6 H -1,3,5-oxathiazine S -oxides followed by ring closure of the resulting intermediates is also reported to yield 1,2,4-thiadiazoles. 15 More recently, Khosropour and Noei described the preparation of 1,2,4-thiadiazoles using 2,4,6-trichloro-1,3,5-triazine, DMSO and polyethylene glycol 400.…”

Synthesis, Characterization, and Reactivity of Novel 6H‐1,3,5‐Oxathiazine S,S‐Dioxides

“…However, the comparable yields were afforded when the aforementioned reactions were carried out at toluene refluxing temperature for 2 h (Table , runs 11–15). In the 1 H NMR spectrum of the aforementioned crude products, we did not observe any peak responsible for 3,5‐diphenyl‐1,2,4‐thidiazole 8 , that was the main product of 4 with silica gel . These results suggest that at high temperature, the compound 5 does not give any deoxygenated product 4 .…”

“…6 H ‐1,3,5‐Oxathiazines 1 were prepared by treating an aryl thioamide with an aliphatic aldehyde and BF 3 .OEt 2 according to the reported procedures . We found that treatment of 1 with 1.1 equiv of m ‐CPBA at 0 °C for 1 h afforded 2 in quantitative yield . Accordingly, we took an attempt to synthesize 3 by two step successive oxidation of 1 using 1.1 equiv m ‐CPBA, but in contrast to our expectation, we have 5 H ‐1,2,4‐oxathiazole S ‐oxide 5 in quantitative yield instead of desired 3 .…”

“…In this way, we already have developed a novel method for generating 1,3‐thiaza‐1,3‐butadiene S ‐oxides (sulfine) B for the synthesis of 5 H ‐1,2,4‐oxathiazoles 4 by thermal cycloreversion of 6 H ‐1,3,5‐oxathiazine S ‐oxides 2 . These findings encouraged us to expand the scope leading to their higher oxidized variants α,β‐unsaturated heterodiene C by thermal cycloreversion of 6 H ‐1,3,5‐oxathiazine S,S ‐dioxides 3 .…”

Optimizing thiadiazole analogues of resveratrol versus three chemopreventive targets

“…In the case of oily compound 3z , it was purified by silica gel chromatography using hexane-ethyl acetate (9:1). Compounds 3a , 33,34 3b , 35,36 3e , 37 3f , 3g , 38 3h , 39 3d , 40 3s , 41 3c , 42 3ff, 43 3jj, 44 3kk 45 have previously been reported.…”