Schiff Base

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Schiff base

[′shif ‚bās]
(organic chemistry)
RR′C=NR″ Any of a class of derivatives of the condensation of aldehydes or ketones with primary amines; colorless crystals, weakly basic; hydrolyzed by water and strong acids to form carbonyl compounds and amines; used as chemical intermediates and perfume bases, in dyes and rubber accelerators, and in liquid crystals for electronics.

Schiff Base

 

any one of a class of organic compounds with the general formula RR′C═NR″, where R and R′ represent hydrogen, an alkyl, or an aryl and R″ is an alkyl or aryl; in the latter case, Schiff bases are also called anils.

Schiff bases are crystalline or oily substances that are insoluble in water and soluble in organic solvents. They are weak bases, forming salts with acids in an anhydrous medium; in aqueous acid solutions they undergo hydrolysis to yield an amine and aldehyde. The majority of Schiff bases are stable in alkaline solutions. Schiff bases undergo hydrogenation to give secondary amines (RR′CH—NHR″) and add on many compounds containing mobile hydrogen, such as (β-dicarbonyl compounds, ketones, and imines. They are produced mainly by the condensation of aldehydes or ketones with primary amines.

The reaction was first completed by H. Schiff in 1864 (hence the name of the compounds). Schiff bases are valuable intermediate products of organic synthesis, for example, in the preparation of secondary amines and various heterocyclic compounds. The Schiff bases known as azomethine dyes are used for dyeing acetate and synthetic fibers; they are also used in color photography to reduce the photosensitivity of photographic emulsions.

References in periodicals archive ?
The complex ToCDS structures included the gem-diamine structure with persulfide-bound Cys356 (Figure S1b), the internal aldimine structure with existing alanine (IAA) with persulfide-bound Cys356 (Figure S1c), and the internal aldimine structure with persulfide-bound Cys356 (PSF) (Figure S1a and Figure 5(c)) as follows the catalytic order of reactions (Scheme 1).
In crystal IV, the internal aldimine structure with persulfide-bound Cys356 was determined at 1.9 A (Figure S1a and Figure 5(c)).
The GD structure allowed us to measure the dihedral angle in two opposite directions, towards the internal aldimine (a positive value) and the external aldimine (a negative value) (Table 2).
Preparation of enantiomerically pure [alpha]-amino acid derivatives from aldimines and tributyltin cyanide or achiral aldehydes, amines, and hydrogen cyanide using a chiral zirconium catalyst," Journal of the American Chemical Society, vol.
In the present work it was found that mischmetall powder (0.3-1.3 mm) is inactive toward aldimines even under reflux.
Only the use of Zn-Cu couple for the asymmetric coupling of aldimines in DMF is documented [9].
Data on the pinacol coupling of the model aldimines with three metal reagents used are presented in Table 1.
Guimond and Fagnou performed a highly efficient rhodium-catalyzed oxidative cross-coupling and [C.sub.4f]-[C.sub.4]/[N.sub.2]- [C.sub.3] cycloaddition of aldimines 68 and 4-octyne 69 en route to 6-fluoro- and 6-trifluoromethylisoquinolines 70a and 70b [47].
Fagnou, "Isoquinoline synthesis via rhodium-catalyzed oxidative cross-coupling/cyclization of aryl aldimines and alkynes," Journal of the American Chemical Society, vol.
Miner et al., "Ethyl lactate as a tunable solvent for the synthesis of aryl aldimines," Green Chemistry, vol.
A convenient, rapid, and one-pot method for the Aza-Diels-Alder reactions of aldimines with dihydropyran or dihydrofuran to afford the corresponding pyrano and furo[3,2-c] quinolines in high yields with high diastereoselectivity in a short period of time has been developed.
Several aldimines (formed in situ from aromatic aldehydes and anilines in THF) reacted smoothly with 2,3-dihydrofuran using nano silica chromic acid (nano-SCA) catalyst to afford the corresponding furano[3,2-c]quinolines as cis/trans mixtures in 87%-92% yield (Scheme 3 and Table 2).