Dichloroquinoline

The order NO2 > Cl, which is known for the reactions of nitro-activated aromatic compounds, is also found for pyridine and quinoline derivatives. In the reaction of 2-chloro-4-nitroquinoline with methoxide ion, only the 4-methoxide derivative is formed, as shown by gas-chromatography, whereas 2,4-dichloroquinoline yields a mixture of the isomeric chloro-methoxy derivatives in comparable amounts. ... 

Table XIV, line 3). The rates are equal (only at 20°) due to a large, compensating difference between the entropies of activation. In piperidino-dechlorination, 4-chloroquinoline (Table XI, line 3) has a higher and a lower rate (by about 200-fold at 20°) than 1-chloroisoquinoline (Table XIV, line 1). This reversal of reactivity and of the relationship of the activation energies is attributed to the factors in amination reactions mentioned above. The relative reactivity of the chloro groups in 2,4-dichloroquinoline with methanolic methoxide is given as a 2 1 rate ratio of 4- to 2-displacement. 

The limited data available for 2,4-dichloroquinoline (Table X, line 9) show a substantially greater rate of methoxylation than for the 2- and 4-chloro analogs (Table X, line 6 and Table XI, line 2), as a result of activation (lowering of E ) by the additional chlorine substituent. Unequal mutual activation (cf. Section III, B, 2) by these substituents is indicated by the rate ratio of 1.9 1 for 4- to 2-substi-tution in the dichloro compound and of 25 1 for the two mono-chloro compounds. 

Dichloroquinoline with ethanolic potassium hydroxide (80°, 2 hr) gave equal amounts (31 and 32% yields) of 4- and 2-ethoxy-lation. In an earlier paper, only the 2-ethoxy product, in unspecifled yield,was reported. The reaction of the dichloro compound with... 

Conditions for controlling the regiochemistry of the addition reactions between benzyl zinc reagents and 2,4-dichloroquinoline under palladium-catalyzed conditions were developed <99JOC453>. Similarly, the regiochemistry of the palladium-catalyzed carbonylation of 4,7-dichloroquinoline was evaluated <99TL3719>. 

Narasimhan (74T4153) introduced a benzofuran type synthesis to avoid a final dehydrogenation step (Scheme 33). 2,4-Dichloroquinoline (186) was prepared by treatment of a mixture of aniline and malonic acid with POCl3. The dichloro compound was converted to... 

The limited data available for 2,4-dichloroquinoline (Table X, line 9) show a substantially greater rate of methoxylation than for the... 

The Sonogashira coupling of 2,4-dichloroquinoline in water with a palladium-carbon catalyst (triphenylphosphine, triethylamine, Cul, 80 °C) shows complete selectivity for the 2-position and Suzuki couplings of 1,3-dichloroisoquinoline are selective for C-1. ... 

Needles from AoOH. M.p. 255°. Sublimes. Prac. insol. most org. solvents. SoL alkalis, alo. HCa. PClg —> 2 4-dichloroquinoline. 

A careful use of solvent effects should be of great assistance in synthetic chemistry. For example, it may be predicted from the solvent effects described above that in the reaction of 2,4-dichloroquinoline with piperidine the a y ratio should increase in the less polar solvents, although the result might be obscured by the mutual influence of the two chlorine substituents. Nitro-activated benzenes support this prediction since ortho para ratios of 4.2 in methanol and 69 in benzene were observed in the reaction of 2,4-dichloronitrobenzene with piperidine. ... 

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