Photochromic amorphous molecular materials based on dibenzothienylthiazole structure

Kawai, Shinnosuke; Nakashima, Takuya; Kutsunugi, Yuuichirou; Nakagawa, Hisako; Nakano, Hideyuki; Kawai, Tsuyoshi

doi:10.1039/b823354c

Cited by 45 publications

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References 68 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%

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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confidence: 99%

Catalyst‐Free Formal Thioboration to Synthesize Borylated Benzothiophenes and Dihydrothiophenes

et al. 2016

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“…Commercially available benzothiophene was successfully methylated at the α‐position at low temperatures and then converted into the corresponding β‐iodo derivative 2 using conventional strong iodination conditions 19. Finally, Li/I exchange at low temperatures and the subsequent nucleophilic substitution onto the perfluorocyclopentene eventually afforded precursor 3 in excellent yields 20.…”

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confidence: 99%

“…Synthetic Procedures: Compounds 1 , 2 , 3 , 4 and 5a were synthesized according reported procedures 18,19…”

Section: Methodsmentioning

confidence: 99%

Enhanced Photochemical Sensitivity in Photochromic Diarylethenes Based on a Benzothiophene/Thiophene Nonsymmetrical Structure

et al. 2014

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Photosensitivity of molecules is one of the central subjects of organic photochemistry. In this article, we present how and why a benzothiophene moiety impacts the photochromic quantum yield for the photochemical pericyclic ring closing of the hexatriene moiety. Two compounds were prepared: a symmetrical one incorporating two fluorenylthiophene units, and its corresponding nonsymmetrical partner, where one of the thiophene units was replaced by a benzothiophene group. Interestingly, the latter presents relatively high cyclization quantum yield (0.74), a value close to the largest one so far reported. Based on crystal structures, VT‐NMR data and DFT calculations, we demonstrate that introducing a benzothiophene in the molecular scaffold induces skeleton stiffening by means of CH–π interactions and steric repulsions, and leads to increased population of the reactive conformer in the ambient conditions.

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“…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][18][19][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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confidence: 99%

“…[11][12][13] These borylated benzothiophenes can then be further elaborated using the wide range of established boron functionalization chemistry. [14][15][16] This reaction employs a commercial boron reagent, B-chlorocatecholborane (ClBcat), removing the need for B-S σ bond formation in starting materials or in intermediates and making the reaction mechanistically distinct for thioboration.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.…”

mentioning

confidence: 99%

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 (Bchlorocatecholborane) 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. Borylative CyclizationsThe first ring-forming thioboration reaction of C-C π bonds is reported. 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. Mechanistic experiments suggest that the operative mechanistic pathway is through boron-induced activation of the alkyne followed by electrophilic cyclization. KeywordsBoron; C-C Activation; Sulfur Heterocycles; Sulfur; Cyclization Thioboration, the addition of sulfur and boron across C-C π bonds, holds promise as an efficient route to synthesize functionalized thioethers. [1] This area of research has focused on Correspondence to: Suzanne A. Blum. HHS Public Access Author ManuscriptAuthor Manuscript Author ManuscriptAuthor Manuscript reagents containing B-S σ bonds that are capable of adding in a direct fashion to π systems. In 2015, Bo, Fernández, and Westcott demonstrated the ability of B-S σ bonds from inhouse synthesized reagents to add across Michael acceptors through boron activation of the carbonyl oxygen (Figure 1a, top), but without generation of a B-C bond for downstream functionalization. [2] In 1993, Miyaura and Suzuki developed a thioboration reaction of B-S σ bonds across alkynes. [3,4] This method similarly employed in-house synthesized reagents containing B-S σ bonds, however it used a carbophilic palladium catalyst to activate the C-C π bond. Protodeboration and in situ Suzuki cross-coupling reactions of these thioboration products were demonstrated, establishing the utility of such synthetic intermediates ( Figure 1a, bottom).In contrast, formal thioboration, wherein the equivalents of boron and sulfur add across a C-C π bond, is underexplored, despite the potential advantages of employing commercially available boron reagents as opposed to the thioboration reagents requiring synthesis, and the plausibility of avoiding a palladium catalyst as previously required in the direct thioboration of alkynes. [3,4] Although little is known about the thiophilicity versus ca...

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Photochromic amorphous molecular materials based on dibenzothienylthiazole structure

Cited by 45 publications

References 68 publications

Catalyst‐Free Formal Thioboration to Synthesize Borylated Benzothiophenes and Dihydrothiophenes

Catalyst‐Free Formal Thioboration to Synthesize Borylated Benzothiophenes and Dihydrothiophenes

Enhanced Photochemical Sensitivity in Photochromic Diarylethenes Based on a Benzothiophene/Thiophene Nonsymmetrical Structure

Catalyst‐Free Formal Thioboration to Synthesize Borylated Benzothiophenes and Dihydrothiophenes

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