- Synthesis and chemistry of 4,5-dihydrothieno[3,2-b]pyrrol-6-ones - A heteroindoxyl
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(Chemical Equation Presented) Flash vacuum pyrolysis (FVP) of 2-acetyl-3-azidothiophene gives 3-methylthieno[3,2-c]isoxazole as the major product at a furnace temperature of 350°C whereas at temperatures above 550°C the new heteroindoxyl 4,5-dihydrothieno[3,2-b]pyrrol-6-one is exclusively formed. The heteroindoxyl exists predominantly as the keto tautomer. It is O-protonated by TFA, N-acetylated by acetic anhydride, N-nitrosated by nitrous acid, and provides an N-methylene Meldrum's acid derivative on treatment with methoxymethylene Meldrum's acid. Reactions of 4,5-dihydrothieno[3,2-b] pyrrol-6-one with diazonium salts, with isatin, and with dimethyl acetylenedicarboxylate take place at the methylene position to provide a hydrazone, an indirubin analogue, and a succinate derivative, respectively. Oxidation of 4,5-dihydrothieno[3,2-b]pyrrol-6-one gives a heteroindigotin, which shows a hypsochromic shift in the UV spectrum, relative to indigotin itself.
- Gaywood, Alexander P.,McNab, Hamish
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supporting information; experimental part
p. 4278 - 4282
(2009/09/08)
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- Factors Affecting the Rates of Thermal Decomposition of Azidothiophenes
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The thermolysis rate of 4-methoxy-1-azidobenzene reveals that the methoxy group increases the rate much less than the endocyclic sulfur does in 3-azidothiophene.With 3-azidothiophene, the neighbouring groups 2-acetyl and 2-nitro enhanced the rate in decalin solution only 5- and 17-fold, respectively, whereas in azidobenzene the corresponding enhancements are 413 and 1060.It is argued that the preferred electron distribution in the transition state for decomposition of 3-azidothiophene is not consistent with that required for effective neighbouring group participation. 2-Cyano and 2-methoxycarbonyl substituents, which are not known as effective neighbouring groups in thermal decompositions of azides, have very little effect on the rate for 3-azidothiophene.
- Dyall, Leonard K.,Suffolk, Peter M.,Dehaen, Wim,L'abbe, Gerrit
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p. 2115 - 2119
(2007/10/02)
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