Fulgide preparation

The carbonylation of 2-methyl-3-butyn-2-oI (50) in benzene gives teraconic anhydride (51). Fulgide (53) (a dimethylenesuccinic anhydride derivative), which is a photochromic compound, can be prepared by the carbonylation of 2,5-dimethyl-3-hexyne-2,5-diol (52)[21], The reaction proceeds under milder conditions when PdlOAc) is used as a catalyst in the presence of iodine [23],... 

Schuster et al. reported that the photochromism of a fulgide could change the helical pitch length of a cholesteric liquid crystal. 27 They added an indolylfulgide 3 (5.2 % w/w) to a cholesteric liquid crystal composed of 4-cyano-4 -pentylbiphenyl 26 (5CB) and 1.35 % (w/w) of a chiral cyclic ether (R)- 27, prepared from (R)-binaphthol. The cholesteric pitch length could be changed reversibly between 30 and 42 pm, after UV and visible light irradiation, respectively. 

Ferrocenyl fulgide 34 gave only E —> Z isomerization without any photochro-mic cyclization reaction.36 Fluorenylidene fulgide 32a was prepared as black crystals, and 32b as deep red crystals. Neither of them were photochromic. However, compound 32c, which was a deep red crystal, was photochromic and gave a blue color when irradiated over a wide range of wavelengths. 

Fulgide 37e, which has been synthesized by Hibino and Ando,46 could be used to prepare Langmuir-Blodgett films having photochromic properties similar to those observed in organic solvents. 

Effenberger and Wonner63 have described the preparation and photochemistry of an anthrylvinyl thiophen fulgide (51). 

Recently Fan et al.,78,79,81 84,86,87 Zhao et al.,so and Fan et al.85 have made an effort to study the molecular design, synthesis, photochromism, and application of pyrryl-substituted fulgides. A series of such fulgides (62) has been prepared by Fan s group, and the photochromic reactions investigated. The molecular structures and photochromic reactions are shown in Scheme 20. 

Oxazolyl (64), 4-pyrazolyl (65), 4-thiazolyl (66), and 4-isoxazolyl (67)-substituted fulgides have been prepared and their photochromic reactions investigated by several groups. The absorption spectra data and quantum yields of their photoreactions are listed in Table 4.19. 

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. 

The first investigations that led to the synthesis, characterization, and properties of fulgides were carried out on phenyl and substituted phenyl fulgides. Therefore it is essential to describe the synthetic procedure for the preparation of phenyl (substituted phenyl) fulgides. This will be beneficial to understanding the later modifications of the synthetic methods for the heterocyclic-substituted fulgides. Some representative examples follow. 

Upon UV irradiation the furyl fulgide undergoes not only cyclization but also an E-Z photoisomerization reaction (Scheme 6). The ratio between the cyclization and the E-Z isomerization depends on the steric hindrance of substituent R. Furyl fulgide derivatives with various R substituents were prepared and the quantum yields were compared [31-34]. The results are summarized in Table 4. 

Selenazolyl fulgides, 2-[5-(4-methyl-2-aryl-l,3-selenazolyl)ethylidene]-3-isopropylidene succinic anhydrides 69, were prepared by reactions of 5-acetyl-l,3-selenazoles with diethyl succinate in alcohol (Scheme 4) <2004RCI451>. 

Fulgides (e.g., 53, see Scheme 15) are capable of photochromic reactions. Yokoyama et al. reported the preparation and subsequent photochromic isomerization of a fulgide which was designed to resist enantiotopomerization [103]. A sample of the resolved fulgide was irradiated (405 nm light in toluene solution) and was observed to come to a pss with a ratio of 19 81. Irradiation with visible light (X > 580 nm) led to the complete recovery of the initial conformation. An advance on this system was made by the same authors, who described the process of diastereomeric photochromism, in which a fulgide derivatized with a binaphthyl auxiliary was allowed to thermally equilibrate, and a photocyclization process carried out [104]. As a result of the relative populations of photoreactive... 

The oxalylfulgides (129) have been prepared and studied. These photochromic yellow dyes undergo ring closure in the conventional manner. The quantum yields for the process and the solvent dependency results are shown below the struetures. " A double Stobbe condensation of 3,5-dimethoxybenzaldehyde with succinic anhydride affords the fulgide (130). This is photochemically reactive and undergoes cyclization to afford a pink cyclic form on irradiation at 366 nm. ... 

A patent application has described the synthesis and photochemical reactivity of the fulgimide derivatives (131). Fulgimides can be prepared by conversion of the fulgides (132) and (133). The resultant products shown photochromic properties. Some new derivatives of fulgimides have been reported with thieno[3,2-b]pyrrole fragments attached to the maleimide. ... 

A fulgide 27 with the benzo-15-crown-5 as the aromatic ring was prepared by Guo et al. Incorporation of alkaline-earth metal cations in the crown-ether moiety resulted in a shift of the absorption of the C-form by more than 40 nm toward shorter wavelengths. 

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