2.4.7- Trimethylquinoline

Antioxidants. The 1,2-dihydroquinolines have been used in a variety of ways as antioxidants (qv). For example, l,2-dihydro-2,2,4-trimethylquinoline along with its 6-decyl [81045-48-9] and 6-ethoxy [91-53-2] derivatives have been used as antio2onants (qv) and stabilizers (68). A polymer [26780-96-1] of l,2-dihydro-2,2,4-trimethylquinoline is used in resins, copolymers, lubricant oils, and synthetic fibers (69). These same compounds react with aldehydes and the products are useful as food antioxidants (70). A cross-linked polyethylene prepared with peroxides and other monomers in the presence of l,2-dihydro-6-ethoxyquinoline produces polymers with a chemically bonded antioxidant (71). 

Chemical antiozonants comprise the second general class of commercial antiozonants. Of the many compounds reported to be chemical antiozonants, nearly all contain nitrogen. Compound classes include derivatives of l,2-dihydro-2,2,4-trimethylquinoline, A/-substituted ureas or thioureas, substituted pyrroles, and nickel or zinc dithiocarbamate salts (see also Antioxidants). The most effective antiozonants, however, are derivatives of -phenylenediamine... 

The principal objection to -PDA antiozonants is their staining characteristics. The lack of suitable alternative antiozonants for light-colored diene mbber articles is one of the outstanding problems in mbber technology. Pew chemical antiozonants outside the class of -PDAs have much commercial importance. One of the few exceptions to this rule is 6-ethoxy-l,2-dihydro-2,2,4-trimethylquinoline [91-53-2] one of the first commercial antiozonants. 

At present, very few compounds are used as thermostabilizers for cured polyethylene. Among them may be listed I,3-dihydro-2,2,4-trimethylquinoline jS-di-naphtyl, -phenylenediamine, zinc mercaptobenzimida-zole [43-45]. 

Methyl groups at positions 2 and 4 in quinoline are selectively oxidized by selenium dioxide (76BSF789). For example, 2,3,8-trimethylquinoline gives 3,8-dimethylquinoline-2-carbaldehyde (Scheme 61). 

The most important chain transfer antioxidants are phenols and aromatic amines (B-81MI11502). They act by donating hydrogen to the peroxy radical with the formation of a stable free radical which does not take part in further chain reactions (equation 4). Two amine antioxidants, used in the rubber industry, are 6-dodecyl-l,2-dihydro-2,2,4-trimethylquinoline (1) and polymeric l,2-dihydro-2,2,4-trimethylquinoline (2). Because of its polymeric structure (2) is thermally stable, has low volatility and is non-blooming, i.e. it shows little tendency to migrate. 

The examples selected to illustrate some of the important cyclisation reactions leading to substituted quinolines and isoquinolines are quinoline [(100), X = H], 8-nitroquinoline [(100), X = N02], 8-hydroxyquinoline [(100), X = OH], 2-methylquinoline (101), 2,4,6-trimethylquinoline (102), 2-phenylquinoline-4-carboxylic acid (103) and 6-methylisoquinoline (104). 

A retrosynthetic analysis for 2,4,6-trimethylquinoline (102) reveals p-toluidine and pentane-2,4-dione. This is an example of the Combes reaction. 

Trimethylquinoline. Add 6g (0.032 mol) of the above enamine, in portions, to 25 ml of concentrated sulphuric acid (d 1.84) contained in a 250-ml conical flask. Swirl the mixture occasionally to ensure thorough mixing. The first portions of the enamine dissolve rather slowly but solution occurs more rapidly with the later portions as the temperature of the mixture increases to 60-70 °C. Heat the reaction mixture on the steam bath for 30 minutes, and then cool the brown solution to room temperature and add it slowly to 250 ml of ice-water in a 1-litre beaker. Add solid sodium carbonate to the solution until it is alkaline. During this addition the quinoline salt tends to separate and the whole mixture may solidify if this happens the mass should be broken up and stirred with a stout glass rod or spatula while the sodium carbonate is added. The quinoline eventually separates as an oil from the alkaline solution. Cool the mixture in an ice-water bath until the quinoline solidifies avoid over-cooling as this will result in the separation of a large... 

A solution of 5-amino-4-chloro-2,6,8-trimethylquinoline (0.22 g, 1 mmol) and 2,6-di-tert-butyl-4-aminophenol (0.35 g, 1.6 mmol) in o-xylene (5 ml) was refluxed for 3 h, then cooled to room temperature, diluted with chloroform (5-7 ml) containing 1 ml of saturated water solution of ammonia and allowed to stand... 

Monohydrochloride, 860 6-Ethoxy-l,2-dihydro-2,2,4-trimethylquinoline, 135, (S3)23 3 -Ethoxy-4-hydroxybenzaldehyde, 496... 

SYNS l,2-DIHYDRO-6-ETHOXY-2,2,4-TRIMETHYL-QUINOLINE l,2-DIHYDRO-2,2,4-TRIMETHYI 6-ETHOXYQUINOLINE EMQ EQ 6-ETHOXY-l,2-DIHYDRO-2,2,4-TRIMETHYLQUINOLINE ETHOXY-QUIN (FCC) ETHOXYQUINE 6-ETHOXY-2,2,4-TRIMETHYDl,2-DIHYDROQUINOUNE NIFLEX NIX-SCALD SANTOFLEX A SANTOFLEX AW SANTOQUIN STOP-SCALD 2,2,4-TRIMETHYL-6-ETHOXY-1.2-DIHYDROQUINOLINE USAFB-24... 

ETHOXY DIGLYCOL see CBROOO 2-ETHOXY DIHYDROPYRAN see EER500 2-ETHOXY-3,4-DIHYDRO-l,2-PYRAN see EER500 2-ETHOXY-3,4-DIHYDRO-2H-PYRAN see EER500 2-ETHOXY-2,3-DIHYDRO-y-PYRAN see EER500 6-ETHOXY-l,2-DIHYDRO-2,2,4-TRIMETHYLQUINOLINE see SAVOOO 1-ETHOXY-3,7-DIMETHYL-2,6-OCTADIENE see GDGIOO... 

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