Hetero-Type Benzannulation Leading to Substituted Benzothio-Phenes

TiCl4 (or SnCl4)-promoted hetero-type benzannulation reactions using various (2,2-dichlorocyclopropyl)(thiophen-2-yl)methanols proceeded smoothly to produce uniquely substituted 4-chlorobenzothiophenes (five examples). The present approach involves the first distinctive thiophene formation from thio...

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Bibliographic Details
Published in:Molecules (Basel, Switzerland) Switzerland), 2021-11, Vol.26 (22), p.7008
Main Authors: Kono, Taro, Sasaki, Ryosuke, Goto, Hideki, Kakuno, Masatoshi, Tanabe, Yoo
Format: Article
Language:English
Subjects:
Alcohol
Aqueous solutions
benzannulation
Benzene
Benzothiophene
Catalysis
Chemical reactions
Chromatography
Cores
Couplings
Cross coupling
Crude oil
gem-dichlorocyclopropane
Hydroxylation
Potassium phosphate
Potassium phosphates
Substitutes
Suzuki–Miyaura cross-coupling
thiophene
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Summary:TiCl4 (or SnCl4)-promoted hetero-type benzannulation reactions using various (2,2-dichlorocyclopropyl)(thiophen-2-yl)methanols proceeded smoothly to produce uniquely substituted 4-chlorobenzothiophenes (five examples). The present approach involves the first distinctive thiophene formation from thiophene cores, in contrast to traditional methods of thiophene formation from benzene cores. The stereocongested (less reactive) Cl position in the obtained 4-chlorobenzothiophenes functioned successfully as the partners of three cross-coupling reactions: (i) a Suzuki–Miyaura cross-couplings using Pd(OAc)2/SPhos/K3PO4 catalysis (seven examples; 63–91%), (ii) a hydroxylation using KOH/Pd(dba)2/tBu-XPhos catalysis (85%), and (iii) a borylation using a B2(pin)2/Pd(dba)2/XPhos/NaOAc catalysis-provided 4-(pin)B-benzothiophene (58%).
ISSN:1420-3049
1420-3049
DOI:10.3390/molecules26227008