benzothiophene
{{Short description|Aromatic organic compound}}
{{chembox
| Verifiedimages = changed
| Watchedfields = changed
| verifiedrevid = 443417324
| Name = Benzothiophene
| Reference = Merck Index, 11th Edition, 9232{{cite web |url=https://www.sigmaaldrich.com/catalog/product/aldrich/357790 |title=Thianaphthene |website=www.sigmaaldrich.com |publisher=Sigma Aldrich |accessdate=12 November 2020}}
| ImageFile_Ref = {{chemboximage|correct|??}}
| ImageFile = Benzothiophene numbering.svg
| ImageSize = 150px
| ImageName = Benzothiophene
| ImageFile1 = Benzothiophene3d.png
| ImageSize1 = 150px
| ImageName1 = Benzothiophene
| PIN = 1-Benzothiophene
| OtherNames = Benzo[b]thiophene
Thianaphthene
Benzothiofuran
|Section1={{Chembox Identifiers
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 35858
| SMILES = s2c1ccccc1cc2
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 6951
| PubChem = 7221
| PubChem_Comment = [b]
| InChI = 1/C8H6S/c1-2-4-8-7(3-1)5-6-9-8/h1-6H
| InChIKey = FCEHBMOGCRZNNI-UHFFFAOYAI
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 87112
| EC_number = 202-395-7
| UNII = 073790YQ2G
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C8H6S/c1-2-4-8-7(3-1)5-6-9-8/h1-6H
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = FCEHBMOGCRZNNI-UHFFFAOYSA-N
| CASNo = 95-15-8
| CASNo_Ref = {{cascite|correct|CAS}}
| RTECS = 202-395-7
}}
|Section2={{Chembox Properties
| C=8 | H=6 | S=1
| Appearance = White solid
| Density = 1.15 g/cm3
| Solubility =
| MeltingPtC = 32
| BoilingPtC = 221
}}
|Section7={{Chembox Hazards
| ExternalSDS =
| MainHazards =
| FlashPtC = 110
| GHSSignalWord = Warning
| GHSPictograms = {{GHS07}}{{GHS09}}
| HPhrases = {{H-phrases|302|411}}
| PPhrases = {{P-phrases|264|270|273|301+312|330|391|501}}
}}
|Section8={{Chembox Related
| OtherCompounds = Thiophene,
Indene, Benzofuran, Indole
}}
}}
Benzothiophene is an aromatic organic compound with a molecular formula C8H6S and an odor similar to naphthalene (mothballs). It occurs naturally as a constituent of petroleum-related deposits such as lignite tar. Benzothiophene has no household use. In addition to benzo[b]thiophene, a second isomer is known: benzo[c]thiophene.{{cite journal|title=Nonclassical Condensed Thiophenes|author1=Cava, Michael P. |author2=Lakshmikantham, M. V. |doi=10.1021/ar50088a005|journal=Accounts of Chemical Research|year=1975|volume=8|issue=4|pages=139–44}}
Benzothiophene finds use in research as a starting material for the synthesis of larger, usually bioactive structures. It is found within the chemical structures of pharmaceutical drugs such as raloxifene, zileuton, and sertaconazole, and also BTCP. It is also used in the manufacturing of dyes such as thioindigo.
Synthesis
Most syntheses of benzothiophene create substituted benzothiophenes as a precursor to further reactions. An example is the reaction of an alkyne-substituted 2-bromobenzene with either sodium sulfide or potassium sulfide to form benzothiophene with an alkyl substitution at position 2.{{cite journal | last1=Sun | first1=Lei-Lei | last2=Deng | first2=Chen-Liang | last3=Tang | first3=Ri-Yuan | last4=Zhang | first4=Xing-Guo | title=CuI/TMEDA-Catalyzed Annulation of 2-Bromo Alkynylbenzenes with Na2S: Synthesis of Benzo[b]thiophenes | journal=The Journal of Organic Chemistry | publisher=American Chemical Society (ACS) | volume=76 | issue=18 | date=16 September 2011 | issn=0022-3263 | doi=10.1021/jo201081v | pages=7546–7550| pmid=21812478 }}
File:2-bromo-alkynylbenzene reacting to form 2-substituted benzothiophene.svg
Thiourea can be used as a reagent in place of sodium sulfide or potassium sulfide.{{cite journal | last1=Kuhn | first1=Marius | last2=Falk | first2=Florian C. | last3=Paradies | first3=Jan | title=Palladium-Catalyzed C–S Coupling: Access to Thioethers, Benzo[b]thiophenes, and Thieno[3,2-b]thiophenes | journal=Organic Letters | publisher=American Chemical Society (ACS) | volume=13 | issue=15 | date=5 August 2011 | issn=1523-7060 | doi=10.1021/ol2016093 | pages=4100–4103| pmid=21732682 }}
File:2-bromo-alkynylbenzene reacting with thiourea to form 2-substituted benzothiophene.svg
In the presence of a gold catalyst, a more complex 2,3-disubstituted benzothiophene can be synthesised.{{cite journal | last1=Nakamura | first1=Itaru | last2=Sato | first2=Takuma | last3=Yamamoto | first3=Yoshinori | title=Gold-Catalyzed Intramolecular Carbothiolation of Alkynes: Synthesis of 2,3-Disubstituted Benzothiophenes from (α-Alkoxy Alkyl) (ortho-Alkynyl Phenyl) Sulfides | journal=Angewandte Chemie International Edition | publisher=Wiley | volume=45 | issue=27 | date=3 July 2006 | issn=1433-7851 | doi=10.1002/anie.200601178 | pages=4473–4475| pmid=16767784 }}
