Phenyl Fulgides

The overall yields, melting points, and spectroscopic properties of some aiyl fulgides are listed in Table 4.1. The general structure is shown in Section 4.1 as model compound 1. 

Fulgide 1 with four different groups R -R, of which at least one group is aryl, can exist as four geometrical isomers. There are two conventions in use for 

Notes The overall yield is based on the phenyl aldehyde or ketone. DMP = 2,4-dimethylphenyl DCP = 2,4-dichlorophenyl TMOP = 3,4,5-trimethoxyphenyl /j-MOP =p - methoxyphenyl. 

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Table 4.1. Overall Yields, Melting Points, and UV Absorption Data for Phenyl Fulgides (1)...

Becker et al.9 found that the absorption spectra of phenyl fulgides at - 196°C showed no characteristic difference from those at room temperature. The temperature independence of aryl fulgides was also reported by Ilge31 in 1986. 

Photochromic Reaction, Substituent Effects, and Fatigue Resistance of Phenyl Fulgides... 

Table 4.5. Substituent Effect on Photochromism of Phenyl Fulgides 289 21...

The isomerization reaction via the excited triplet state was only found in the EE <- ZZ and EZ <-> ZE sensitized reactions. The EoZ isomerization is a basic photochemical reaction. Different excited states have different chemical behaviors. The results can be summarized i n Scheme 29 for phenyl fulgides. 

Scheme 29. E<- Z photoisomerization of phenyl fulgides (R, R1 are hydrogen or alkyl groups ...

The electrocyclic reactions of phenyl fulgides and l,8a-DHNs can be photo-induced by a conrotatory process. The electrocyclic ring-opening reaction of cyclohexadiene systems (l,8a-DHNs) can also be induced thermally via a disrota-tory process. 

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. 

H. D. Ilge and H. Schutz, Photochemistry of fulgides. 18, -nuclear resonance of phenyl fulgides, J. 

H. D. Ilge, C. Drawert, J. Suehnel, and R. Paetzold, Photochemistry of fulgides. XII. Electronic and steric substituent effects on the UV/visible absorption spectra of phenyl fulgide, J. Prakt. Chem., 326, 233-247 (1984). 

H. D. Ilge, Photochemistry of phenyl fulgides. XX. Absence of activation barriers for photoisomerization reactions in the excited singlet state of extremely sterically hindered a, 8-di-(4-alkoxypheny 1) fulgide isomers, J. Photochem., 33, 333-347 (1986). 

Furyl fulgide 20 (Eq. (7)) is the first known example of thermally irreversible photochromic molecules. Although phenyl fulgides such as 21 have been known to show photochromic reactions, photogenerated dihydronaphthalene derivatives such as 21C (Eq. (8)) are thermally unstable and undergo irreversible side reactions, i.e., 1,5-hydrogen shifts to produce 1,2-dihydonaphthalene derivatives [23-26]. This... 

An n.m.r. study of phenyl fulgides has been published. Heller and his coworkers have continued their study of photochromic systems. In the present report the... 

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