Thiophene-2-carboxylic acid

Thiophene-2-carboxylic acid is an organic compound with the formula SC₄H₃CO₂H. It is one of two monocarboxylic acids of thiophene, the other being thiophene-3-carboxylic acid.^[1] Copper(I) thiophene-2-carboxylate is a catalyst for Ullmann coupling reactions.

Thiophene-2-carboxylic acid

Names
Other names 2-thenoic acid; tenoic acid; Rhinotrophyl
Identifiers
CAS Number	527-72-0 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:71241
ChEMBL	ChEMBL1222314
ChemSpider	10250
ECHA InfoCard	100.007.659
EC Number	208-423-4
KEGG	D08568
PubChem CID	10700
UNII	3FD00JX53J
CompTox Dashboard (EPA)	DTXSID2060177
InChI InChI=1S/C5H4O2S/c6-5(7)4-2-1-3-8-4/h1-3H,(H,6,7) Key: QERYCTSHXKAMIS-UHFFFAOYSA-N
SMILES C1=CSC(=C1)C(=O)O
Properties
Chemical formula	C5H4O2S
Molar mass	128.15 g·mol−1
Appearance	white solid
Melting point	125–127 °C (257–261 °F; 398–400 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Synthesis

It can be prepared by the oxidation of thiophene-2-carboxaldehyde or, more practically, 2-acetylthiophene.^[2]

Applications and reactions

Suprofen, which is produced from thiophene-2-carboxylic acid, is the active ingredient in some eye drops.^[2]

Upon treatment with LDA, thiophene-2-carboxylic acid undergoes double deprotonation to give the 5-lithio derivative, a precursor to many 5-substituted derivatives.^[3]

Thiophene-2-carboxylic acid has been widely studied as a substrate in coupling reactions and olefinations.^[4][5]