- Intramolecular Catalysis in the Detritiation of 3-Carboxy-2-(acetyl)thiophene
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The kinetics of detritiation of 3-carboxy-2-(acetyl)thiophene have been studied at 50 deg C in aqueous buffer systems as well as at 25 deg C in sodium hydroxide solutions.The results, when compared with similar investigations on the corresponding 3-iodo- and 3-thiomethyl-2-(acetyl)thiophenes, serve to show the importance of intramolecular catalysis by the carboxylate group.Estimates of the efficiency of the catalysis have been obtained, these are similar in magnitude to the values previously reported for derivatives of 2'-carboxyacetophenones.
- Buncel, Erwin,Jones, John R,,Sowdani, Kassim,Spinelli, Domenico,Consiglio, Giovanni,Arnone, Caterina
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p. 559 - 562
(2007/10/02)
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- Condensed Isothiazoles. Part 5. Thienoisothiazoles and Thienoisothiazoles
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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).
- Clarke, Kenneth,Fox, William Richard,Scrowston, Richard M.
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p. 1029 - 1037
(2007/10/02)
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