Clemizole

Clemizole

Clinical data
ATC code	None
Identifiers
IUPAC name 1-[(4-Chlorophenyl)methyl]-2-(pyrrolidin-1-ylmethyl)benzimidazole
CAS Number	442-52-4
PubChem CID	2782
ChemSpider	2680
UNII	T97CB3796L
KEGG	D01705
ChEBI	CHEBI:52140
ChEMBL	ChEMBL1407943
NIAID ChemDB	033090
CompTox Dashboard (EPA)	DTXSID0046939
ECHA InfoCard	100.006.486
Chemical and physical data
Formula	C19H20ClN3
Molar mass	325.84 g·mol−1
3D model (JSmol)	Interactive image
SMILES Clc1ccc(cc1)Cn3c(nc2ccccc23)CN4CCCC4
InChI InChI=1S/C19H20ClN3/c20-16-9-7-15(8-10-16)13-23-18-6-2-1-5-17(18)21-19(23)14-22-11-3-4-12-22/h1-2,5-10H,3-4,11-14H2 Key:CJXAEXPPLWQRFR-UHFFFAOYSA-N

Clemizole is an H₁ antagonist.

Synthesis

Benzimidazoles substituted with an alkylamine at position 2 have a venerable history as H₁ antihistaminic agents. The standard starting material for many benzimidazoles consists of phenylenediamine, or its derivatives.

Clemizole synthesis:

Reaction of that compound with chloroacetic acid can be rationalized by invoking initial formation of the chloromethyl amide. Imide formation with the remaining free amino group closes the ring to afford 2-chloromethyl benzimidazole (3). Displacement of halogen with pyrrolidine affords the alkylation product. The proton on the fused imidazole nitrogen is then removed by reaction with sodium hydride. Treatment of the resulting anion with α,4-dichlorotoluene gives the H₁ antihistaminic agent clemizole (5).

See also

• Chlormidazole