Schiff bases s. Azomethines

Saturation s. Hydrogenation Scavenger s. Water scavenger Schiff bases s. Azomethines Schdnberg reaction 8, 172 suppl. 21... 

Schiff bases s. Azomethines Schlotterbeck s. Buchner Schmidt reaction 17, 524 —, amines from carboxylic acids 19, 305 20, 366 —, lactams from ketones, cyclic, ring expansion... 

Novikov, M.S. Khlebnikov, A.F. Besedina, O.V. Kostikov, R.R. The first example of intramolecular cycloaddition of carbene-derived azomethine ylides in a domino reaction of difluorocarbene with Schiff bases. Tetrahedron Lett. 2001, 42, 533-535. 

Metal chelates are preser t in the complexes of Schiff bases of amino-(X = NR2), hydroxy- (X = O), and mercapto- (X = S) derivatives of monoheteroaromatic five-membered systems, azoles, and azines. A few publications on the complexes of azomethines of the monoheteroaromatic five-membered systems have appeared only recently. The X-ray structural study of copper(II) bis(2-N-n-octyliminomethyl)benzo[ 7]thio-phene-3-olate) 199 (04ZNK1696) is interesting in the sense that its square-planar structure is complemented by an extended octahedral one due to the intermolecular contacts of the thiophene sulfur with the copper site. Among the azole complexes, azomethine derivatives of p3Tazole (Equation (32)) prevail (05RCR193). There are several types of coordination units (N,N-, N,0-, N,S-, N,Se-) created by variation of the donor sites X in position 5 of the pyrazole ring. When X = O, S, Se, tautomer b is realized, whereas when X = NR, tautomer a predominates (Equation (32)). However, irrespective of the type of tautomer, in the chelates the coordination units have practically equalized bonds. 

Aromatic nitro compounds are often strongly colored. They frequently produce characteristic, colored, quinoid derivatives on reaction with alkali or compounds with reactive methylene groups. Reduction to primary aryl amines followed by diazotization and coupling with phenols yields azo dyestuffs. Aryl amines can also react with aldehydes with formation of Schiff s bases to yield azomethines. 

Preparation with aliphatic amines, on the other hand, may promote side reactions, converting portions of a pigment to compounds that are somewhat soluble in toluene. Toluene is the most important solvent for publication gravure printing inks. This preparative method reduces the viscosity of the printing ink. The pigment is thus partially converted to a soluble azomethine (Schiff s base), which is formed by reaction between the acetoacetic arylide and an aliphatic amine [5] ... 

Aldehydes react with primary amines to give the so-called azomethines (Schiff s bases), by elimination of water (p. 161), e.g. 

Skraup s synthesis involves the elimination of water. Thus acrolein will he formed. It may react with aniline to form an azomethine (Schiff s base) (I), hut more probably the base adds itself to the C=C double bond (II) ... 

A new route to mono- and dioxo derivatives of 1,3-oxazine was given by Martin et a/.96,97 addition of 2 moles of ketene to the C=N of azomethines. (This reaction was described by Staudinger98-100 in 1906, but piperidinedione structures were assigned to these compounds.) When the Schiff s base PhCH=NEt reacted with 2 moles of dimethyl-ketene a good yield of a derivative of 2-isopropylidenetetrahydro-l,3-... 

The reaction of 1,2-diaminonitrobenzenes with aldehydes is a widely accepted synthetic route to nitrobenzimidazoles [57, 62,63,66, 350,372-383], This reaction passes sequentially through a stage of the formation of azomethines (Schiff s base) and benzimidazolines. On oxidation the latter forms the corresponding benzimidazole derivatives (Scheme 2.44). 

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