2- Methylquinolines, reaction with acyl chlorides

Silica gel catalyzed the reaction of 2-methylquinolines 354 with acyl chlorides under solvent-free conditions using MWI to give 2-ketomethylquinolines 355 in 53 91% yields within 4 min (Scheme 71). The reaction of 2-methylquinoline 354 (R = H) with benzoyl chloride without irradiation was unsuccessful at room temperature and at 200 °C (01TL4363). 

Pyrazolo[3,4-Z)]pyridines, the 7-chloro-6-fluoro-2,4-dimethylquinoline and its mercapto-thiadiazolyl or oxadiazolyl quinolines 21 were prepared via Diels-Alder reaction conversion of methyl 2-(3-oxo-3-phenylpropenylamino)benzoate into 3-benzoyl-l.S -quinolin-4-one 22 . A mixture of aniline derivatives and malonic ester gave a variety of 3-aryl-4-hydroxyquinolin-2(l//)-ones 23. Condensation of isatins with ketones afforded quinoline-4-carboxylic acids. 2-Aryl-l,2,3,4-tetrahydro-4-quinolinones 22 and carbazolylquinolone were also prepared. The substitution of 2-chloroquinoline gave the 2-substituted quinolines. Basic alumina has catalyzed the C-C bond formation between 2-hydroxy-1,4-naphthoquinone and 2-chloroquinoline derivative to give 21. Reaction of organic halides with 8-hydroxyquinolines gave the respective ethers. The azodye derivatives of 21 were prepared in the absence of solvent. Silica gel catalyzed the formation of 2-ketomethylquinolines from reaction of 2-methylquinolines with acyl chlorides. 

The reaction of N,N- dimethylaniline with pyridine (equation 55) should also be considered in this category. Enamines usually attack acylated N- oxides at position 2 unless it is blocked, as in 2-methylquinoline 1-oxide, when attack takes place at C-4. Methyl /3-aminocrotonate attacks quinoline and isoquinoline AT-oxides at the position a to the N- oxide function in the presence of tosyl chloride (78JHC1425). However, pyridine and 2-methylpyridine 1-oxides react at the 4-position (equation 142). A low yield of by-product (242) is formed in each case, probably as a result of self-condensation of methyl /3-aminocrotonate. 4-Hydroxyquinoline 1-oxide is exceptional in that it reacts with an enamine in the presence of tosyl chloride at the /3-position (Scheme 170) (B-71MI20500). 5-Amino-3-methylisoxazole reacts with quinoline 1-oxide at the a-position, and the product can be degraded, to afford ultimately 2-methylquinoline (Scheme 171) (78CPB2759). 

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