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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/07/01 11:57:22」(JST)

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General structure of an azomethine

General structure of a Schiff base (narrow definition)

A Schiff base, named after Hugo Schiff, is a compound with a functional group that contains a carbon-nitrogen double bond with the nitrogen atom connected to an aryl or alkyl group.^[1] Schiff bases in a broad sense have the general formula R¹R²C=NR³, where R is an organic side chain. In this definition, Schiff base is synonymous with azomethine. Some restrict the term to the secondary aldimines (azomethines where the carbon is connected to a hydrogen atom), thus with the general formula RCH=NR'.^[2] Schiff bases can also be referred to as imines.

The chain on the nitrogen makes the Schiff base a stable imine. A Schiff base derived from an aniline, where R³ is a phenyl or a substituted phenyl, can be called an anil.^[3]

Synthesis

Schiff bases can be synthesized from an aliphatic or aromatic amine and a carbonyl compound by nucleophilic addition forming a hemiaminal, followed by a dehydration to generate an imine. In a typical reaction, 4,4'-diaminodiphenyl ether reacts with o-vanillin:^[4]

A mixture of 4,4'-Oxydianiline 1 (1.00 g, 5.00 mmol) and o-vanillin 2 (1.52 g, 10.0 mmol) in methanol (40.0 mL) is stirred at room temperature for one hour to give an orange precipitate and after filtration and washing with methanol to give the pure Schiff base 3 (2.27 g, 97%)

Biochemistry

Schiff bases are common enzymatic intermediates where an amine, such as the terminal group of a lysine residue reversibly reacts with an aldehyde or ketone of a cofactor or substrate. The common enzyme cofactor PLP forms a Schiff base with a lysine residue and is transaldiminated to the substrate(s).^[5] Similarly, the cofactor retinal forms a Schiff base in rhodopsins, including human rhodopsin (via Lysine 296), which is key in the photoreception mechanism.

An example where the substrate forms a Schiff base to the enzyme is in the fructose 1,6-bisphosphate aldolase catalyzed reaction during glycolysis and in the metabolism of amino acids.

Coordination chemistry

Schiff bases are common ligands in coordination chemistry. The imine nitrogen is basic and exhibits pi-acceptor properties. The ligands are typically derived from alkyl diamines and aromatic aldehydes.^[6]

Schiff base ligands

Copper(II) complex of the Schiff base ligand salicylaldoxime.

Salen is a common tetradentate ligand that becomes deprotonated upon complexation.

Jacobsen's catalyst is derived from a chiral salen ligand.

Chiral Schiff bases were one of the first ligands used for asymmetric catalysis. In 1968 Ryōji Noyori developed a copper-Schiff base complex for the metal-carbenoid cyclopropanation of styrene.^[7] For this work he was later awarded a share of the 2001 Nobel Prize in Chemistry.

References

^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "Schiff base".
^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "azomethines".
^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "anils".
^ Jarrahpour, A. A.; M. Zarei (February 24, 2004). "Synthesis of 2-({[4-(4-{[(E)-1-(2-hydroxy-3-methoxyphenyl)methylidene amino}phenoxy)phenyl imino}methyl)- 6 -methoxy phenol". Molbank M352. ISSN 1422-8599. Retrieved February 22, 2010.
^ Eliot, A. C.; Kirsch, J. F. (2004). "PYRIDOXALPHOSPHATEENZYMES: Mechanistic, Structural, and Evolutionary Considerations". Annual Review of Biochemistry 73: 383–415. doi:10.1146/annurev.biochem.73.011303.074021. PMID 15189147. edit
^ R. Hernández-Molina, A. Mederos "Acyclic and Macrocyclic Schiff Base Ligands" in Comprehensive Coordination Chemistry II 2003, Pages 411–446. doi:10.1016/B0-08-043748-6/01070-7
^ H. Nozaki, H. Takaya, S. Moriuti, R. Noyori (1968). "Homogeneous catalysis in the decomposition of diazo compounds by copper chelates: Asymmetric carbenoid reactions". Tetrahedron 24 (9): 3655–3669. doi:10.1016/S0040-4020(01)91998-2.

English Journal

Synthesis, spectral, antitumor, antioxidant and antimicrobial studies on Cu(II), Ni(II) and Co(II) complexes of 4-[(1H-Benzoimidazol-2-ylimino)-methyl]-benzene-1,3-diol.

El-Wakiel N1, El-Keiy M2, Gaber M3.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy.Spectrochim Acta A Mol Biomol Spectrosc.2015 Aug 5;147:117-23. doi: 10.1016/j.saa.2015.03.020. Epub 2015 Mar 19.
A new Schiff base of 2-aminobenzimidazole with 2,4-dihydroybezaldehyde (H3L), and its Cu(II), Ni(II) and Co(II) complexes have been synthesized and characterized by elemental analyses, molar conductance, thermal analysis (TGA), inductive coupled plasma (ICP), magnetic moment measurements, IR, EI-mas
PMID 25827773

Synthesis of Small 3-Fluoro- and 3,3-Difluoropyrrolidines Using Azomethine Ylide Chemistry.

McAlpine I, Tran-Dubé M, Wang F, Scales S, Matthews J, Collins MR, Nair SK, Nguyen M, Bian J, Alsina LM, Sun J, Zhong J, Warmus JS, O'Neill BT.
The Journal of organic chemistry.J Org Chem.2015 Jul 17;80(14):7266-74. doi: 10.1021/acs.joc.5b00853. Epub 2015 Jun 24.
Here, we report accessing small 3-fluoropyrrolidines and 3,3-difluoropyrrolidines through a 1,3-dipolar cycloaddition with a simple azomethine ylide and a variety of vinyl fluorides and vinyl difluorides. We demonstrate that vinyl fluorides within α,β-unsaturated, styrenyl and even enol ether syst
PMID 26057617

Modular Synthesis of Pyrazolones Using an Alkene Aminocarbonylation Reaction.

Lavergne K1, Bongers A1, Betit L1, Beauchemin AM1.
Organic letters.Org Lett.2015 Jul 17;17(14):3612-5. doi: 10.1021/acs.orglett.5b01719. Epub 2015 Jul 1.
A variety of pyrazolones were synthesized from enol ethers and hydrazones using a reaction sequence involving aminocarbonylation of enol ethers followed by nucleophile-induced aromatization of the azomethine imines intermediates. Using bases to catalyze the in situ formation of imino isocyanates all
PMID 26126788

Japanese Journal

1,3-双極子を活用する複素環合成の新展開

有機合成化学協会誌 73(1), 65-75, 2015
NAID 130004749156

Desymmetrization of 1,4-pentadien-3-ol by the asymmetric 1,3-dipolar cycloaddition of azomethine imines

Chemistry - A European Journal 20(7), 2058-2064, 2014-02-10
NAID 120005368204

LEWIS ACID CATALYZED DIASTEREOSELECTIVE 1,3-DIPOLAR CYCLOADDITION BETWEEN DIAZOACETOACETATE ENONES AND AZOMETHINE YLIDES (Dedicated to Professor Victor Snieckus on the occasion of his 77th birthday)

Heterocycles : an international journal for reviews and communications in heterocyclic chemistry 88(2), 1039-1049, 2014-01-01
NAID 40019927945

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