Tetrahydrofuran-2-one Derivatives

Compounds 79 can be prepared by reaction of fulgides with a molar equivalent of malonitrile in the presence of diethylamine, followed by dehydration with acetyl chloride. A typical procedure is described in Section 4.7. 

Another dicyanomethylene derivative of fulgide 81 was also reported. On irradiation with white light, the purple compound 81 underwent an intramolecular [4 + 4] photocyclization reaction to give colorless adducts, which underwent the reverse reaction thermally or photochemically.35 The results demonstrated that molecular modification of fulgide molecules can significantly affect the photochromic properties of fulgide family compounds. 

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In the same year, Heller et al.3 reported a new kind of photochromic compound - dicyanomethylene derivatives of fulgide. According to the nomenclature system of the International Union of Pure and Applied Chemistry (IUPAC), they should be named as 5-dicyanomethylene-tetrahydrofuran-2-one derivatives, as shown in formula 8. 

Tetrahydrofuran-2-one derivatives were previously prepared by the author by cyclization of (E)-3-(4-fluorophenyl)-3-(4-sulfamoyl-phenyl)-2-(2-hydroxylethyl)propen-2-enoic acid, (I), and are discussed (3). 

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