Skraup s synthesis

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) ... 

Quinoline is a colorless liquid, b.p. 239°, with a characteristic odor. It possesses the properties of a tertiary amine base forming salts as pyridine does. It is present with the latter in coal tar and in bone oil but is usually not obtained from these sources being prepared by Skraup s synthesis. 

The preparation of 8-hydroxyquinoline has long been known. The basis of the preparation is Skraup s synthesis, which essentially involves the reaction of primary aromatic amines with unsaturated carbonyl compounds and the oxidation of the... 

On the other hand molybdenum species, due to their Lewis acidity, catalyse mainly the condesation reactions similar to those proposed in the mechanism o-f the acid catalysed Skraup s synthesis o-f quinolines -from aldehydes and anilines ... 

Bismuth triflate catalyzes the synthesis of 1,2-dihydroquinolines in an improved version of Skraup s procedure [74]. Accordingly, treatment of aniline with... 

Sulphuric acid is the condensing agent used. The reaction might be compared with the preceding reaction and with Skraup s quinoline synthesis (see p. 165). 

REACTION SKRAUP S QUINOLINE SYNTHESIS Example Quinoline... 

The classical method of quinoline synthesis involves Skraup s procedure. " However, it requires a large amount of H2SO4 at elevated temperature and the reaction often becomes violent. 

Scheme 7. The classical Skraup quinoline synthesis (a) and Fukuyama s modified approach (b) using /V-aryl-AZ-sulfonylaminopropionaldehydes (56).

Doebner-von Miller reaction is a variant of the Skraup quinoline synthesis (page 509). Therefore, the mechanism for the Skraup reaction is also operative for the Doebner-von Miller reaction. The following mechanism is favored by Denmark s mechnistic study using C-labelled a,P-unsaturated ketones. ... 

Both 5-hydroxyquiQoline [578-67-6] and S-hydroxyquiaoline [148-24-3] have been prepared ia good yields by the acid hydrolysis of the appropriate aminoquiaoline at temperatures of 180—235°C (124). The latter compound has been prepared ia several different ways, including sulfonation-fusion of quiaoline. Hydrolysis of 8-chloroquinoline [611-33-6] gives a 93% yield, whereas 80% is obtained ia a modified Skraup synthesis with o-aminophenol (125,126). 

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