Synthesis of Benzothiophens

Scheme 68 Two-step microwave-assisted synthesis of benzothiophenes...

Pinney et al. reported the synthesis of benzothiophene CA4 analogs and an example synthesis is given in Scheme 38 [83]. Benzothiophene (145) was produced by reacting aromatic thiol 146 with a-bromoacetophenone 147 to generate the sulfide 148. Compound 148 was then cyclized to the benzothiophene 149 using polyphosphoric acid and heat. Formation of 145 was achieved by Friedel-Crafts aroylation of 149 with the methoxybenzoyl chloride 144. 

In 06MI2, aminothiazole 259 was synthesized. Recently, Japanese researchers have used this method for the synthesis of benzothiophene analogs 260 and 261 (09NJC1368). 

Unlike in the case of the preparation of indoles and benzofuranes, the synthesis of benzothiophenes from o-ethynyl-thiophenols is not known. A close analogy was reported by Larock, where phenylacetylene was coupled with 2-iodothioanisole. Ring closure of the formed o-ethynyl-sulfide was initiated by the addition of different electrophiles. The reaction led to the formation of the benzothiophene core bearing the electrophile in the... 

SYNTHESIS OF BENZOTHIOPHENES BY FUSION OF SIX-MEMBERED CARBOCYCLIC RINGS TO THIOPHENES... 

Further new applications of the Meerwein arylation include the synthesis of benzothiophenes [94] and benzylmethyl ketones [95]. 

Cyclisation of 2-arylthio- or 2-aryloxy-aldehydes, -ketones or -acids via intramolecular electrophilic attack on the aromatic ring, with loss of water, creates the heterocyclic ring this route is a common method for the ring synthesis of benzothiophenes. 

Synthesis of benzothiophenes can also be accomplished by an acid-promoted intramolecular cyclization reaction. The 3-substituted thiophene undergoes a rearrangement under acidic conditions to produce 2-substituted benzothiophenes. ... 

Recent advances in the synthesis of benzothiophenes 12THC(29)347. Synthesis and apphcations of highly luminescent dithieno[3,2- 2, 3T((] phospholes 13SL920. 

A facile and selective palladium-catalyzed carbonylative domino synthesis of benzothiophenes was developed by Alper and Zeng in 2011 [273]. 2-Carbon-ylbenzo[Z ] thiophene derivatives were produced from 2-gem-dihalovinylthiophe-nols in 24-73 % yields (Scheme 2.39). This protocol involved an intramolecular C-S coupling/intermolecular carbonylation cascade sequence and allowed for access to various highly functionalized benzo[h]thiophenes. 

Synthesis of Benzothiophens by Ring-closure Reactions.—A review of the chemistry of benzothiophens, covering the period 1952—1968, has appeared. ... 

The cyclization of o-bcnzylthiobenzyl cyanides (326) with aluminium bromide gives 2-aminobenzo[6]thiophens (327). A new synthesis of benzothiophens is based upon the reaction of o-mercapto-aromatic ketones or their xanthates (328) with dimethylsulphonium methylide. The... 

Scheme 2.149 Synthesis of benzothiophenes from o-bromo-ethynylbenzenes.

Scheme 2.151 Pd-catal3 ed synthesis of benzothiophenes from em-dihalovinyl thiophenols.

Intermolecular C—S bond formation has been exploited in a recent synthesis of benzothiophenes utilizing o-alkynylhaloarene substrates (Scheme 24.38,... 

Synthesis of Benzothiophens by Ring-closure Reactitms.— Thiophenols react slowly (5-22 days) with dimethyl acetylenedicarboxylate in methanol to... 

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