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Issue 10, 1995
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Photochromic heterocyclic fulgides. Part 8. The condensation of 2,6-dichlorobenzaldehyde with diethyl [1-(2,5-dimethyl-3-furyl)ethylidene]succinate to give 6-chloro-2-(2,5-dimethyl-3-furyl)-1H-benzocycloheptene-3,4-dicarboxylic anhydride and photochromic (7S,7aS)-7-(2,6-dichlorophenyl)-2,4,7a-trimethyl-7,7a-dihydrobenzofuran-5,6-dicarboxylic anhydride

Abstract

The dark red photochromic (7S,7aS)-7-(2,6-dichlorophenyl)-2,4,7a-trimethyl-7,7a-dihydrobenzofuran-5,6-dicarboxylic anhydride has been synthesised by the Stobbe condensation of 2,6-dichlorobenzaldehyde with diethyl [1-(2,5-dimethyl-3-furyl)ethylidene]succinate in the presence of potassium tert-butoxide in tert-butyl alcohol. When tert-butyl alcohol is replaced by toluene, 6-chloro-2-(2,5-dimethyl-3-furyl)-1H-benzocycloheptene-3,4-dicarboxylic anhydride is produced. Use of an aprotic solvent provides a new general method of preparing 2-substituted 6-chloro-1H-benzocycloheptene-3,4-dicarboxylic anhydrides via a mechanism involving nucleophilic substitution of chlorine in 2,6-dichlorobenzaldehyde, followed by intramolecular condensation.

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Article type: Paper
DOI: 10.1039/P19950001323
Citation: J. Chem. Soc., Perkin Trans. 1, 1995,0, 1323-1325
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    Photochromic heterocyclic fulgides. Part 8. The condensation of 2,6-dichlorobenzaldehyde with diethyl [1-(2,5-dimethyl-3-furyl)ethylidene]succinate to give 6-chloro-2-(2,5-dimethyl-3-furyl)-1H-benzocycloheptene-3,4-dicarboxylic anhydride and photochromic (7S,7aS)-7-(2,6-dichlorophenyl)-2,4,7a-trimethyl-7,7a-dihydrobenzofuran-5,6-dicarboxylic anhydride

    H. G. Heller, C. J. Morgan and M. J. Ottaway, J. Chem. Soc., Perkin Trans. 1, 1995, 0, 1323
    DOI: 10.1039/P19950001323

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