91505-29-2Relevant academic research and scientific papers
Condensed Isothiazoles. Part 5. Thienoisothiazoles and Thienoisothiazoles
Clarke, Kenneth,Fox, William Richard,Scrowston, Richard M.
, p. 1029 - 1037 (2007/10/02)
2,3-Disubstituted thiophens containing a sulphur function (SH, SMe, or SCN) and a carbonyl group (CHO or Ac) have been prepared and converted into thienoisothiasoles.Methods used to prepare 1,2-benzisothiazoles are often inapplicable in the thiophen series.For example, an (E)-methyl (2-methylthio-3-thienyl) O-p-nitrobenzoylketoxime (6) in hot diethylene glycol or acetic acid gave the corresponding 3-acetamido-2-methylthiothiophen (15); in concentrated sulphuric acid at - 5 deg C, it gave the Beckmann rearranged product (15) and a thienothiazole (19).Similarly, (E)-methyl (3-methylthio-2-thienyl) O-p-nitrobenzoyl ketoxime (42) gave 2-methylthienothiazole with concentrated sulphuric acid, but with acetic acid it gave the thienoisothiazole (43) and 2-acetamido-3-methylthiothiophen.Heating the (E)-2-mercaptothiophen-3-carbaldoxime (27) in an inert solvent gave the corresponding thienoisothiazole (14); the (E)-3-mercaptothiophen-2-carbaldoxime (47) cyclised in hot AcOH-Ac2O, to give the thienoisothiazole (44).Thienoisothiazoles were also prepared by treating a methyl (2-mercapto-3-thienyl) ketone (21) with chloramine and by heating a 2-iminothieno-3,1,4-oxathiazepine (29) in an inert solvent.The products obtained by selective S-alkylation of 3,5-bis(sodiomercapto)isothiazole-4-carbonitrile with ethyl bromoacetate and iodomethane were cyclised, to give 4-aminothienoisothiazole derivatives (34) and (36).
