Synthesis of Photochromic Diarylethenes

Diverse Studies from Japanese Project Cluster 11.4.14.1 Synthesis of Photochromic Diarylethenes 

The University of Kyoto, the MCPT research group, and Yamada Chemical developed an effective method for the synthesis of photochromic diarylethenes through the generation of heteroaryHithiums and subsequent reaction with octafluorocyclopentene 

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Following similar trials with the formation of diarylbenzenes [63-65], the same research group has reported a multistep synthesis of photochromic diarylethenes using a microflow system that contained two linked micromixers and microreactors (MRi 2) [66]. Similarly to the previously reported linked microreactors, the reactors used in this setup were made of stainless steel tubes and T-shaped micromixers. Initial experiments were conducted in two steps in a continuous sequence to afford symmetrical octasubstitued diaryUiexafluoro cyclopentene (Scheme 29). 

Ushiogi Y, Hase T, linuma Y et al (2007) Synthesis of photochromic diarylethenes using a microflow system. Chem Commun 28 2947-2949... 

In 2011, Schipper [94] reported the synthesis of potent organic electronics material through a palladium-catalyzed C-H arylation of thiophenes. For example, compound 76, a donor material in heterojunction solar cells [96], and compound 77, a fluorescent marker for in vivo optical imaging [97], can be rapidly synthesized by C-H/C-X coupling of the corresponding thiophenes and aryl halides without any prefunctionalization of the thiophene moieties. Shinokubo and Itami [95] demonstrated the synthesis of photochromic diarylethenes 78 through two palladium-catalyzed C-H arylations of thiophenes. 

Asai T, Takata A, Nagaki A, YosMda J (2012) Practical synthesis of photochromic diarylethenes in integrated flow microreactor systems. ChemSusChem 5 339—350. doi 10.1002/... 

Recently, the synthesis of photochromic compounds containing two or more diarylethene fragments bound either directly or through linkers has been performed. Scheme 32 illustrates one approach to 96 containing two hexafluorocyclopentene-bridged dihetarylethene fragments (05JACS8922). 

The photoreactivity of DTE derivatives in the crystalline state is of special interest because of their potential usefulness for holographic and three-dimensional memories. In crystals, molecules are regularly oriented and packed in fixed conformations. In many cases, free rotation is inhibited. Therefore, the photoreactivity in the crystalline phase is dependent on the space for free rotation of the thienyl rings and the conformation formed in the crystal lattice. Several reports on the synthesis of metal complexes of photochromic diarylethenes and their photo-reactivity in the single-crystalline phase or the photoswitching of the coordination structure have been reported. These studies demonstrate that complexation to metal ions does not prohibit the photochromic reactions of the diarylethene units in the single-crystalline phase. 

Figure 11.26 Synthesis scheme of photochromic diarylethenes. (a) Generation of heteroaryllithiums through the Br-Li exchange reaction of heteroaryl bromides and (b) the reaction of octafluorocyclopentene with heteroaryllithium.

Irie M, Uchida K (1998) Synthesis and properties of photochromic diarylethenes with heterocyclic aryl groups. BuU Chem Soc Jpn 71 985-996... 

Irie, M., Diarylethenes for memories and switches, Chem. Rev., 100,1685,2000 Irie, M. and Mohri, M., Thermally irreversible photochromic systems. Reversible photocychzation of diarylethene derivatives, /. Org. Chem., 53, 803, 1998 Irie, M. and Uchida, K., Synthesis and properties of photochromic diarylethenes with heterocyclic aryl groups. Bull. Chem. Soc. Jpn., 73, 985, 1998 Tsivgoulis, G.M. and Lehn, J.M., Photoswitched and functionalized olifothiophenes synthesis and photochemical and electrochemical properties, Chem.-Eur. ]., 2,1399,1996. 

Topics which have formed the subjects of reviews this year include theoretical studies of the photochemistry of thiiranes, photoaddition of amines to aryl olefins and arenes, the synthesis of heterocyclic compounds, photoamination directed towards the synthesis of heterocycles, selective addition of organic dichalcogenides to carbon-carbon unsaturated bonds, photocyclisation mechanisms of c/5-stilbene analogues, synthetic utility of the photocyclisation of aryl-and heteroarylpropenoic acids, photochromic diarylethenes, spiropyrans, cy-clophanes, and polycondensed aromatics," photochromic organic media, photophysics and photochemistry of P-carbolines, and the photochemical synthesis of macrocycles.Chirality switching by light has also been described. ... 

Topics of relevance to the content of this chapter which have been reviewed during the year include photoactive [2]rotaxanes and [2]catenanes, photochemical synthesis of macrocycles, phototransformations of phthalimido amino acids, photoaddition reactions of amines with aryl alkenes and arenes, photoreactions between arenenitriles and benzylic donors, photostability of drugs, polycyclic heterocycles from aryl- and heteroaryl-2-propenoic acids, photoreactions of pyrroles, photoamination reactions in heterocyclic synthesis, switching of chirality by light, photochromic diarylethenes for molecular photoionics and solid state bimolecular photoreactions. 

Several reviews have been published within the year which are of general relevance to the photoreactions of aromatic compounds. The subjects of these reviews include photochemistry in ionic liquids and in isotropic and anisotropic media, organic synthesis utilizing photoinduced electron-transfer reactions," heteroatom-directed photoarylation processes, photochromism, and photochemical molecular devices. Reviews more directly pertinent to the sections in the present chapter include those of the photoisomerization of five-membered heteroaromatic azoles, the photocycloaddition of benzene derivatives to alkenes, Diels-Alder additions of anthracenes, advances in the synthesis of polycyclic aromatic compounds, diarylethene-based photochromic switches, the photo-Fries rearrangement, and the application of Diels-Alder trapping of photogenerated o-xylenols to the synthesis of novel compounds. " A number of chapters in the two recently published handbooks of photochemistry and photobiology and in the revised edition of the text on photochromism are also pertinent to the current subject matter. 

K. Uchida, A. Takata, M. Saito, A. Murakami, S. Nakamura, M. Irie, Synthesis of novel photochromic films by oxidation polymerization of diarylethenes containing phenol groups, Adv. Funct. Mater., 13, 755-762 (2003). 

N. ImpagnatieUo, A. Heynderickx, C. Moustrou, A. Samat, Synthesis and photochromic properties of functional diarylethenes with a [1, 3]dithiol-2-one (thione) bridging unit. Mol. Cryst. Liq. Cryst., 430, 243-248 (2005). 

Photochromic LC polymers are usually synthesized via the copolymerization of mesogenic monomers with photochromic mesogenic or nonmesogenic monomers similar to the synthesis of chiral LC polymers (Figure 19), hut, instead of a chiral monomer, a photochromic monomer is used as a mle, its concentration varies from 10 to 60mol.%. Diverse derivatives of azobenzene, spiropyran, diarylethenes, dnnamates, and coumarin-containing derivatives are used as photoactive fragments. 

Krayushkin MM, Kalik MA, Dzhavadov DL, Mattynkin AYu, Firsov AV, Ilzhinov BM (1999) Photochromic diarylethenes. 2. Synthesis and photochromic properties of 5,5 alkylthio (alkylsulfonyl)-substituted l,2-bis(2-aIkylthien-3-yl) pafluoiocyclopaitenes. Izv Acad Nauk Ser Khim 979-982... 

Pu S, liu G, Shen L, Xu J (2007) Efficient synthesis tmd properties of isomeric photochromic diarylethenes having a pyrrole unit. Otg Lett 9 2139-2142. doi 10.1021/ol070622q... 

Nakashima, H. and Irie, M. (1997) Synthesis of silsesquioxanes having photochromic diarylethene pendant groups. Macromd. Rapid Commun., 18, 625-633. 

Yam reported the synthesis and sensitized photochromic properties of a versatile diarylethene containing 1,10-phenanthroline ligand and their metal complexes (Re [72, 73], Pt [74]). Unlike other studies where the ligand is covalently connected to the DTE unit, phenl displays an original design in which the ligand itself is part of the dithienyl framework. 

Fluorescent photochromes of diarylethene series Synthesis and properties 13UK511. 

Synthesis and properties of novel photochromic poly(methyl methacrylate[Pg.245]

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