Amidine
Amidines are organic compounds with the functional group RC(NR)NR2, where the R groups can be the same or different. They are the imine derivatives of amides (RC(O)NR2). The simplest amidine is formamidine, HC(=NH)NH2.
Examples of amidines include:
- DBU
- diminazene
- benzamidine
- Pentamidine
- Paranyline
Preparation
A common route to primary amidines is the Pinner reaction. Reaction of the nitrile with alcohol in the presence of acid gives an iminoether. Treatment of the resulting compound with ammonia then completes the conversion to the amidine.[1] Instead of using a Bronsted acid, Lewis acids such as aluminium trichloride promote the direct amination of nitriles.[2] They are also generated by amination of an imidoyl chloride.[3] They are also prepared by the addition of organolithium reagents to diimines, followed by protonation or alkylation.
Dimethylformamide acetal reacts with primary amines to give amidines:[4]
- Me2NC(H)(OMe)2 + RNH2 → Me2NC=NHR + 2 MeOH
Acid-base chemistry
Amidines are much more basic than amides and are among the strongest uncharged/unionized bases.[5][6]
Protonation occurs at the sp2-hybridized nitrogen. This occurs because the positive charge can be
Applications
Several drug or drug candidates feature amidine substituents. Examples include the antiprotozoal Imidocarb, the insecticide amitraz , the anthelmintic tribendimidine, and xylamidine, an antagonist at the 5HT2A receptor.[8]
Formamidinium (see below) may be reacted with a metal halide to form the light-absorbing
Nomenclature
Formally, amidines are a class of
Derivatives
Formamidinium cations
A notable subclass of amidinium ions are the formamidinium
Amidinate salts
An amidinate salt has the general structure M+[RNRCNR]− and can be accessed by reaction of a
See also
- Guanidines — a similar group of compounds where the central carbon atom is bonded to three nitrogen atoms.
- Imidazolines contain a cyclic amidine.
References
- .
- .
- .
- .
- ^ Roche VF. Improving Pharmacy Students’ Understanding and Long-term Retention of Acid-Base Chemistry. American Journal of Pharmaceutical Education. 2007;71(6):122.
- ISBN 978-0-19-850346-0.
- ISBN 3-527-30655-2.
- PMID 7905649.
- doi:10.1039/B104110J.
- .
- PMID 11414862.
- ISBN 9780470065105.