5,6,7,8-Tetrahydro-8-quinolone

Scheme 6.47 Synthesis of 2-aryl-l, 2,3,4-tetrahydro-4-quinolones via cyclization reaction on clay.

Aryl-l,2,3,4-tetrahydro-4-quinolones 348 can be dehydrogenated to the corresponding 4-quinolones 349 by using IBD-KOH/MeOH (94SC2167) (Scheme 89). Surprisingly, the expected product a-hydroxydimethylacetal 350 is not obtained. 

The tetrahydro-2-quinolone (212) affords a very small yield of 1,2-cycloadduct on irradiation with diphenylacetylene in methanol.189 The two major products are the 1,4-dimer and the pentacyclic derivative (213), arising presumably by intramolecular photocycloaddition... 

Keywords 2 -aminochalcone, microwave irradiation, 2-aryl-1,2,3,4-tetrahydro-4-quinolone... 

Selig, P. and Bach, T. (2006) Photochemistry of 4-(2 -aminoethyl) quinolones enantioselective synthesis of tetracyclic tetrahydro-laH-pyrido [4, 3 2,3]-cydobuta[l,2-c] quinoline-2,11 (3H, 8H)-diones by intra- and inter-molecular [2 + 2] photocydoaddition reactions in solution. Journal of Organic Chemistry, 71, 5662—5673. 

In a model reaction used to support the structure identification of a neutral polyaza cleft for enolate complexations, the disubstituted dihydropyrrolo[2,3-/i]quinoline (51) was prepared by alkylation of 7-bromo-5,6,7,8-tetrahydro-8-quinolone with ethyl 3,3-diamino-2-propenoate (Equation (24)) <91JA9687>. The regioisomeric residence of the two substituents in this product was supported by 13C—13C shift-correlated NMR spectroscopy. 

For the preparation of 4-(1.2.3.4-tetrahydroquinolino)-phenol 17 three different procedures were worked out [Eqs. (6)-(8)]. 17 was prepared by reacting N-p-methoxyphenyl-anthranilic acid with acetic anhydride and subsequent saponification to l-p-methoxyphenyl-4-hydroxy-2-quinolone, reaction withPOCl3 to form l-p-methoxyphenyl-4-chloro-2-quinolone, hydrogenation to l-(p-methoxy-phenyl)-3.4-dihydro-2-quinolone, splitting the ether with HBr to l-(p-hydroxy-phenyl)3.4-dihydro-2-quinolone, and reduction with LiAlH4 [Eq. (6)J. Another synthetic possibility was the reaction of p-anilinophenol with (3-propiolactone and subsequent cyclization to l-(p-acetoxyphenyl)2.3-dihydro-4-quinolone 18. The next step, the Wolff-Kishner reduction, led directly to the desired product [Eq. (7)]. The third way, the direct amination of p-iodoanisole with 1.2.3.4-tetrahydro-quinoline and the subsequent splitting of 4-(1.2.3.4-tetrahydro-quinolino)-anisol with HBr was the best one [Eq. (8)]. Saponification of l-(p-acetoxyphenyl>2.3-... 

Alkoxy-2-arylquinolines 2-Aryl-l,2,3,4-tetrahydro-4-quinolones undergo dehydrogenation and O-methylation when treated with PhI(OTs)OH, HCIO, and HCjOMejj. 

Heterocyclic Synthesis. - The reactions of phosphorus ylides with phenan-threne-9,10-quinone (113) have been used to prepare phenanthrene [9,10-x]-fused compounds with four, five, and six membered heterocyclic rings. (E)-4-carbethoxymethylene-l,2,3,4-tetrahydro-2-quinolones 114 have been obtained from the stereoselective reaction of 3-hydroxy-1,2,3,4-tetrahydroquinoline-2,4-diones and ethyl(triphenylphosphoranylidene)acetate. A -trifluoroacetylanilines 115 react with Ph3P=C02Et producing enamine derivatives 116 as a mixture of (E)- and (Z)-isomers. Enamines 116 are useful precursors for the synthesis of indoles and quinolones. 

The reaction of pentafluorobenzoylpyruvic acid (as well as the reaction of aroyl-pyruvic acid) with ethanolamine in dioxane yields 3-pentafluorobenzoylmethylene-morpholin-2-one. Due to the presence of ortho-fiuorine in the aromatic ring, the latter is capable of further cyclization forming 4-oxo-7,8,9,10-tetrafluoro-l,2,4, 5-tetrahydro[l,4]oxazino[4,3-<2]-4-quinolone (94JFC(69)119, 94IZV279) (Scheme 63). 

Aminochalcones, which are readily available, provide easy access to 2-aryl-l,2,3,4-tetrahydro-4-quinolones in yet another solvent-free cydization reaction (internal Michael addition) using KIO clay under microwave irradiation conditions [179] the products are valuable precursors for medicinally important quinolones (Scheme 8.70). 

An easy access to 2-aryl-4-quinolone (85) has been achieved from 2-aryl-l,2,3,4-tetrahydro-4-quinolone (86) using hypervalent iodine as the oxidizing agent (Scheme 47) (94SC(24)2167). 

Thummel and coworkers have synthesized dipyrido[4,3-fc 5,6-fc]acri-dines 304 from the condensation of 8-amino-7-quinolinecarbaldehyde 302 with 5,6,7,8-tetrahydro-8-quinolone (303) and their ruthenium(II) complexes (Scheme 65) (96IC5953). 

To a mixture of 4 mL acetic acid and 1.5 mL acetic anhydride was added 0.5 g 4-methyl-5,6,7,8-tetrahydro-5-(hydroxyimino)-2-hydroxyquinoline (3.0 mmol). The solution was saturated with anhydrous HCl gas and then held at reflux for 18 h. At the end of the reaction period, the solution had become dark, whereupon it was cooled, diluted with water, and allowed to stand for several hours. The white precipitate that formed was washed with water and crystallized from alcohol to provide 0.30 g 4-methyl-5-acetamido-2-quinolone, in a yield of 53%, m.p. 355°C. 

Ozonolyses of tetrahydro-lH-pyrido-[4,3-fe]-indoles resulted in the formation of a nine-membered keto-lactam, which could either be isolated or in situ cyclized to dihydropyrrolo[3,2-( ]quinolones, which can be derivatized by electrophilic aromatic substitution, selectively on the pyrrole moiety. In the ozonolysis reaction, alkyl cin-noline betaines were formed as side products, most likely via Cl side products. ... 

Singh, O.V., KapU, R.S. 1993. A new route to 2-aryM-quinolones via thallium(III) p-tol-ylsulphonate mediated oxidation of 2-aryl-l,2,3,4-tetrahydro-4-quinolones. Synthetic Communications 23 277-283. 

Application of [2- C]IAA to the cotyledon of etiolated 5-day-old broad been (Vicia faba L. cv Chukyo) seedlings resulted in accumulation of radioactive substances in the root primordia and in the stele of the basal part of the roots [24, 25]. Two metabolites being more polar than lAA-Asp accounted for 70-80% of total radioactivity in the root after 24-h treatment, and they were not extracted with ether in acid pH. After hydrolysis with 2 M HCl or 7 M NaOH, their radioactive moieties were extracted with ether, but they did not coincide with lAA. We purified the two substances from Vicia roots and identified them as 3-(0-)S-glucosyl)-2-indolone-3-acetylaspartic acid (Glc-DIA-Asp) and 3-hydroxy-2-indolone-3-acetylaspartic acid (DIA-Asp) [26, 27]. The DIA moiety is converted into 2-quinolone-4-carboxylic acid (QCA) by acid hydrolysis and the UV spectrum of QCA is quite different from that of DIA, which is in contrast with the conversion of OxIAA into l,2,3,4-tetrahydro-2-quinolone-4-carboxylic acid without accompanying large spectral change. 

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