ChemInform Abstract: Photochromic 2‐Pyrrylfulgides.

Abstract

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Synthesis and highly efficient light-induced rearrangements of diphenylmethylene(2-benzo[b]thienyl)fulgides and fulgimides

“…Indeed, in the case of diphenylmethylene(aryl)fulgides the whole process (including the formation of a colored intermediate and its gradual decoloration) usually required 12-14 hours [14,17]. Even for the most similar in structure diphenylmethylene(indolyl)fulgide, the cyclization occurred only after ex-tended irradiation (τ > 10 4 s) [16], whereas for fulgides 3Z and 3E this time is at least two orders of magnitude less (Figure 3). Although the appearance of 3Z and 4-(3-methoxybenzo[b]thiophen-2-yl)-9-phenyl-4,4a-dihydronaphtho[2,3-c]furan-1,3-dione (9I) shown in Scheme 4 was not directly registered in the absorption spectra (Figure 3), their existence was evidenced by the data obtained in earlier studies [5,6,[14][15][16].…”

“…Even for the most similar in structure diphenylmethylene(indolyl)fulgide, the cyclization occurred only after ex-tended irradiation (τ > 10 4 s) [16], whereas for fulgides 3Z and 3E this time is at least two orders of magnitude less (Figure 3). Although the appearance of 3Z and 4-(3-methoxybenzo[b]thiophen-2-yl)-9-phenyl-4,4a-dihydronaphtho[2,3-c]furan-1,3-dione (9I) shown in Scheme 4 was not directly registered in the absorption spectra (Figure 3), their existence was evidenced by the data obtained in earlier studies [5,6,[14][15][16]. Moreover, the occurrence of the Z/E-photoisomerization concomitant of the first stage of the rearrangement can be traced at small irradiation times (less than 1-2 min) of fulgide 3Z in acetonitrile solution with light of 436 nm.…”

“…Under exposure of solutions or crystals of thus prepared hetaryl(aryl)-substituted dihydrofuran-2,5-diones to UV light, those bearing an isopropylidene fragment attached to the furandione moiety, usually demonstrate positive photochromism as the result of conversion to their deeply colored cyclic isomers. However, fulgides containing a diphenylmethylene group are capable of negative photoinduced rearrangements [14][15][16][17].…”