Synthesis and Photochemical Reactions of Photochromic Terarylene Having a Leaving Methoxy Group

Nakagawa, Hisako; Kawai, Shinnosuke; Nakashima, Takuya; Kawai, Tsuyoshi

doi:10.1021/ol802969b

Cited by 51 publications

(30 citation statements)

References 36 publications

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“…Primary competing strategies for the synthesis of borylated benzothiophenes include lithiation/electrophilic trapping [17,18] and transition metal-catalyzed borylation of the benzothiophene core. [19,20] The formal thioboration strategy described herein provides complementary functional group tolerance to these other borylation methods, and also furnishes the benzothiophene core in the same synthetic step.…”

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confidence: 99%

“…The slower reactivity was attributed to competitive coordination of the amide to boron. Notably, functional groups that cannot be tolerated by existing methods of borylation of benzothiophenes (i.e., lithiation/electrophilic trapping or Pd-catalyzed Miyaura borylation) [17–20] were tolerated by these thioboration reaction conditions (e.g., substrates 3f–3h , 3j , 3m , 3n ). Thus, this thioboration reaction provided access to borylated benzothiophenes that had limited accessibility through traditional methods.…”

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Catalyst‐Free Formal Thioboration to Synthesize Borylated Benzothiophenes and Dihydrothiophenes

et al. 2016

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The first ring-forming thioboration reaction of C–C π bonds is reported. This catalyst-free method proceeds in the presence of a commercially available external electrophilic boron source (B-chlorocatecholborane) in good to high yields. The method is scalable and tolerates a variety of functional groups that are intolerant of other major borylation methods. The resulting borylated benzothiophenes participate in a variety of in situ derivatization reactions, showcasing that these borylated intermediates do not need to be isolated prior to downstream functionalization. This methodology has been extended to the synthesis of borylated dihydrothiophenes. Mechanistic experiments suggest that the operative mechanistic pathway is through boron-induced activation of the alkyne followed by electrophilic cyclization, as opposed to S–B σ bond formation, providing a mechanistically distinct pathway to the thioboration of C–C π bonds.

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Catalyst‐Free Formal Thioboration to Synthesize Borylated Benzothiophenes and Dihydrothiophenes

et al. 2016

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“…all, a reaction between 3-iodo-4-bromo-1,8-naphthalic anhydride (5) and 5-methyl-2-phenylthiazole-4-boronic acid (8) was used to give a semicoupled product (10). After simple liquid-liquid extraction that gave the crude product (10), the second Suzuki coupling reaction yielded compound 12.…”

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The synthesis of new 3,4-(bisaryl)-1,8-naphthalimide and 2,3-(bisaryl)-7 H -benzimidazo[2,1-a]benzo[d]isoquinolin-7-one compounds and an investigation of their photochromic properties

Orhan¹,

Köse²,

Yazan³

2018

Turk J Chem

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Three new photochromic compounds, 3-(2,5-dimethyl-3-thienyl)-4-(2-phenyl-5-methyl-4-thiazolyl)-1,8-napht-were synthesized and their photochromic properties were studied. Compound 1-O was synthesized by two consecutive Suzuki coupling reactions using 2,5dimethylthiophene-3-boronic acid and 5-methyl-2-phenylthiazole-4-boronic acid. Photochromic compounds 2-O and 3-O were prepared by multistep reactions starting with 3-iodo-4-bromo-1,8-naphthalic anhydride and 2,5-dimethylthiophene-3-boronic acid or 2-phenyl-5-methylthiazole-4-boronic acid. All photochromic compounds showed a color change from colorless (or light yellow) to blue-green, purple, or orange colors (depending on the nature of the structures) on exposure to UV light at 365 nm in ethyl acetate solutions. The colored solutions can be reversed to the original colorless (or light yellow) solution by exposure to visible light at 530 nm.

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“…[9] Other forms of selective chemical reactivity for the ring-closed forms of diarylethenes and terarylenes have been reported as photo-gated reactions. [11] This elimination reaction quantitatively proceeded either in highly polar solvents such as acetone or in the presence of acid. Recently, the authors have reported the elimination of methanol from the ring-closed form of a terarylene derivative to form condensed fluorescent aromatics which never returned to the original open-ring isomer with visible light irradiation (Scheme 1).…”

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Subsequent Chemical Reactions of Photochromic 4,5‐Dibenzothienylthiazoles

2012

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4,5‐Dibenzothienylthiazole derivatives having leaving groups at the reactive 2‐positions of benzothiophene rings have been synthesized, and their photochromic ring‐closing reaction followed by spontaneous elimination and substitution reactions have been studied. A 4,5‐dibenzothienylthiazole having an ethoxy group and a hydrogen atom at each 2‐position of the benzothienyl ring underwent elimination to generate a condensed aromatic structure upon the addition of acid. 4,5‐Dibenzothienylthiazoles having an ethoxy or methyl groups at the 2‐position of the benzothienyl rings showed photochromism both in hexane and in methanol solutions with photocyclization quantum yields as high as 60 %. Upon the addition of acid to the methanol solutions of closed‐ring isomers of dibenzothienylthiazoles, the substitution of the ethoxy group with a methoxy group occurred. The generation and rearrangement of the carbocation intermediate formed by elimination of the ethoxy group from the closed‐ring isomers were apparent from the chemical structure of methoxy‐substituted products.

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Synthesis and Photochemical Reactions of Photochromic Terarylene Having a Leaving Methoxy Group

Abstract: Photochromic terarylene having a methoxy group and hydrogen as the leaving units at the photochemical reaction center carbon atoms has been synthesized. This molecule shows irreversible photochemical reaction affording a highly fluorescent condensed aromatic molecule.

Cited by 51 publications

References 36 publications

Catalyst‐Free Formal Thioboration to Synthesize Borylated Benzothiophenes and Dihydrothiophenes

Catalyst‐Free Formal Thioboration to Synthesize Borylated Benzothiophenes and Dihydrothiophenes

The synthesis of new 3,4-(bisaryl)-1,8-naphthalimide and 2,3-(bisaryl)-7 H -benzimidazo[2,1-a]benzo[d]isoquinolin-7-one compounds and an investigation of their photochromic properties

Subsequent Chemical Reactions of Photochromic 4,5‐Dibenzothienylthiazoles

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