2-ethyl-3-methylquinoline

Diallylaniline is converted exclusively into 2-ethyl-3-methylquinoline when heated with a catalytic amount of Co2(CO)8 under an atmosphere of CO (Equation 120) <2003JOC3563>. A [4+2] cycloaddition of iV-arylaldimines with vinyl ethers catalysed by ytterbium(lll) triflate gave quinoline derivatives in good yields (Equation 121) <1995S801>. 

Diallylaniline, when heated with a catalytic amount of CojfCOlg under an atmosphere of CO, produces 2-ethyl-3-methylquinoline exclusively. Further examination of this reaction found that diallylaniline is in fact a source of the allyl group in this transformation <03JOC3563>. 

Further studies on regioselectivity, solvent effects, temperature effects, and catalyst loadings were also conducted [27]. A series of 2-ethyl-3-methylquinolines was obtained and substituents were added at the 5-, 6-, 7- and 8 positions. As seen in Table 6.2, introduction of an electron-donating group favored product formation, whereas electron-withdrawing groups inhibited product formation. 

Table 6.3 Yields for the conversion of diallylaniline to 2-ethyl-3-methylquinoline with different catalyst loadings and solvents. T = 105°C, 1 atm CO, [diallylaniline] = 0.2M.

It also catalyses oxidation reaetions with an oxidant, e g. the methylene group in cyclopropylmethyl-compounds to a carbonyl group in the presence of metaperiodate [Hasegawa et al. Chem Lett (Jpn) 1385 1985, Carlsen et al. J Org Chem 46 3936 1981, cf Review Gore Platinum Metals Rev 27 111 1983]. It catalyses the synthesis of 2-ethyl-3-methylquinolines from primary aromatic arrtines arrd triallylamine [Cho et al. Tetrahedron Lett 40 1499 1999], and has been used for the selective hydrogenation of urrsatuiated aldehydes [Fujita et al. J Catal 255 95 2004]. 

CO atmosphere affords 2-ethyl-3-methylquinoline through dehydrogena-tive cyclization (Scheme 10.3a). Furthermore, the same catalytic system also promotes a cross-coupling of Af-benzyhdeneaniline and Af,Af-diallylanihne to afford 2-phenyl-3-methylquinoline, where the latter reactant serves as a donor... 

Conra.d-Limpa.ch-KnorrSynthesis. When a P-keto ester is the carbonyl component of these pathways, two products are possible, and the regiochemistry can be optimized. Aniline reacts with ethyl acetoacetate below 100°C to form 3-anilinocrotonate (14), which is converted to 4-hydroxy-2-methylquinoline [607-67-0] by placing it in a preheated environment at 250°C. If the initial reaction takes place at 160°C, acetoacetanilide (15) forms and can be cyclized with concentrated sulfuric acid to 2-hydroxy-4-methylquinoline [607-66-9] (49). This example of kinetic vs thermodynamic control has been employed in the synthesis of many quinoline derivatives. They are useful as intermediates for the synthesis of chemotherapeutic agents (see Chemotherapeuticsanticancer). 

Syndesmon thalictroides Hoffm. Abnormal fasciated specimens yielded 3-methylquinoline-4-carboxylic acid and methyl and ethyl fsocarbostyril-3-carboxylates (Beattie, J.. Amer. Chem. Soc., 1908, 40, 415). 

These early contradictions were eventually resolved and led to the correction by Knorr of his initially proposed structure. While Conrad and Limpach described the reaction of aniline 1 with ethyl acetoacetate 5 which ultimately yielded 4-hydroxy-2-methylquinoline (7) via initial reaction of the amine with the ketone, Knorr described... 

The proposed mechanism for the Conrad-Limpach reaction is shown below. Condensation of an aniline with a 3-keto-ester (i.e., ethyl acetoacetate 5) with loss of water provides enamino-ester 6. Enolization furnishes 10 which undergoes thermal cyclization, analogous to the Gould-Jacobs reaction, via 6n electrocyclization to yield intermediate 11. Compound 11 suffers loss of alcohol followed by tautomerization to give 4-hydroxy-2-methylquinoline 7. An alternative to the proposed formation of 10 is ejection of alcohol from 6 furnishing ketene 13, which then undergoes 671 electrocyclization to provide 12. 

The situation is more complex for 364 if R — methyl or benzyl, for then a series of compounds is formed. These have been described as as azepinobenzimidazoles,210 but are probably cyclobuta[4,5]pyrrolo-[l,2-a]benzimidazoles (cf. 369 and compounds from DM AD and 2-methylquinoline). Minor products from these reactions may have structure 365, and similar compounds have been obtained from 2-benzimidazolylacetonitrile and ethyl 2-benzimidazolylacetate.208... 

C12H13N 3-ethyl-6-methylquinoline 105688-74-2 557.65 49.450 1.2 23973 C12H140 isopropyl styryl ketone 3160-32-5 461.90 40.236 2... 

MBH acetates have been conveniently transformed into multi-substituted quinolines and cyclopenta[g]quinolines by the reaction with nitroethane or ethyl cyanoacetate via a successive 5 N2 -5NAr elimination strategy. As shown in Scheme 4.182, reaction of MBH acetates (618 and 619) in DMF, in the presence of potassium carbonate and nitroethane at 50-75 °C, afforded the desired substituted 8-methylquinolines 620 in 80-92% yields or substituted 9-methyl cyclopenta[g]quinoline-6-ones 622 in 85-94% yields in a short time (3-4 h). Similarly, substituted 8-cyanoquinolines 621 were obtained from the reaction of MBH acetates 618 with ethyl cyanoacetate at relatively higher temperatures (110-125 °C) and for longer times ( 10 h) in 50-60% yields. 

EVisms from Et20 or pet. ether. M.p. 57°. B.p. 26S-9°/711 mm. Sol. EtOH, EijO, CgHg. Spar. sol. H2O. CrOg —> 3-methylquinoline-2-carboxylic acid. Sn + HCl —>- 3-methyl-2-ethyl-1 2 3 4-tetrahydroquinoline. 

The gold-catalyzed formal cycloaddition reactions of 2-ethynylbenzyl ethers with 8-methylquinoline oxide and ethyl diazoacetate led to a skeletal rearrangement of the benzo[c]furan motif through an attack of the diazo compound on the initial oxonium species in the alkyne activation route, followed by a Roskamp-type rearrangement and ring closure (13AGE7559). 

---