Ethoxy-quinoline

Examples from preparative chemistry indicate the possible occurrence of special alpha-e ects in several other cases. The different reaction of 2- and 4-ethoxy quinolines with a thiol yielding carbostyril and a 4-arylthio derivative, respectively, may indicate the intervention of structures such as 17 in the transition state of the 2-isomer. 

Indirect deactivation by an alkoxy group is apparent in the sluggish reaction of 4-butoxy-2-chloroquinoline with w-butylamine (EtOH, 5 hr, 180°, but not at 80°). The chloro group in 2-chloro-4-ethoxy-quinoline is more reactive than that in the 4-chloro-2-ethoxy isomer toward alkoxides or amines in spite of the usually more effective para indirect deactivation in the former. For kinetic data on quinolines see Tables X and XI, pp. 336 and 338, respectively. 

See vnaer Hydraciylic Acid and Lactic Acid. 5-EthoxyquinaldUixie 2-Methyl-5-ethoxy, quinoline)... 

Reaction of 1-ethoxycyclohexene (34) with dichlorocarbene gives 1-ethoxy-7,7-dichloronorcarane (35) in 87 % yield. Rearrangement of dichlorocyclo-propane (35) in hot quinoline results in loss of both chlorine atoms to give l-ethoxycyclohepta-l,3,5-triene (37) in 37% yield. Hydrolysis of enol ether (37) with a very small quantity of hydrochloric acid in methanol produces cyclohepta-3,5-dienone (38) in 91 % yield. ... 

Reaction of dibromocyclopropane (39) with hot quinoline gives 1-ethoxy-cyclohepta-l,3,5-triene (37) in 32% yield. Dihalocyclopropanes prepai ed from larger ring enol ethers do not react with hot pyridine but afford products with hot quinoline formed by transannular reactions. 

Reaction of 2,4,7-trichloroquinoline with sodium methoxide (65°, 30 min) yielded an equal mixture of 2,7-dichloro-4-methoxy- (40%) and 4,7-dichloro-2-methoxy-derivatives (31%). The activating effect of the chloro groups is evident from the inertness of 4-chloro-quinoUne to methoxide ion at 65°. Alteration of the relative reactivity by cationization of the azine ring is again noted here in the acid-catalyzed hydrolysis (dilute HCl, 100°, 1.5 hr) of the trichloro compound to give 72% of the 2-hydroxylation product.Similarly, acid-hydrolysis of the alkoxy group proceeds much more readily in 2-ethoxy-4-chloro- than in 4-ethoxy-2-chloro-quinoline. ... 

Quinoxalinyl, 4-cinnolinyl, and 1-phthalazinyl derivatives, which are all activated by a combination of induction and resonance, have very similar kinetic characteristics (Table XV, p. 352) in ethoxylation and piperidination, but 2-chloroquinoxaline is stated (no data) to be more slowly phenoxylated. In nucleophilic substitution of methoxy groups with ethoxy or isopropoxy groups, the quinoxaline compound is less reactive than the cinnoline and phthalazine derivatives and more reactive than the quinoline and isoquinoline analogs. 2-Chloroquinoxaline is more reactive than its monocyclic analog, 2-chloropyrazine, with thiourea or with piperidine (Scheme VI, p. 350). 

Angularly annelated H- -methy 1-8-ethoxy carbonyl-9-oxo-6,9-dihydrotriazolo [5,4-/]quinolone is formed preferably 164 over the sterically less hindered (9-0X0 group vs 1-methyl group) linearly annelated triazolo[4,5-g]quinoline 165 in a reaction starting from 6-aminoethylene substituted 1-methyIbenzotriazole. Hydrolysis of the cyclization product produced the corresponding acid 166 (Scheme 52) (94CCC1145). 

The first attempted synthesis of a benzo[ ]thiepin derivative was the solvolysis of 7,7-dichloro-3,4-benzo-2-thiabicyclo[4.1,0]heptene (19)20). Unfortunately, the reaction of 19 in hot quinoline led to 2-chloronaphthalene which suggested the reaction mechanism as shown below. In the case of the reaction of l,l-dichloro-7b-ethoxy-... 

Ar-quinolin-2-yl)imino]propionates by injection or sublimation at 530°C yielded a mixture of 3-amino- and 3-ethoxy-l//-pyrimido[l,2-rz]quinolin-l-ones <2004AJC577>. An oxidative cascade for the biomimetic formation of the pyoverdine chromophore was supported by incubation of 2-[(4-hydroxyphenyl)- and 2-[(2-(3,4-dihydroxipheny-l)ethyl]-l,4,5,6-tetrahydropyrimidines with polyphenol oxidase or Pseudomonas extract to afford a mixture of 8,9-dihydroxy-2,3-dihydro- and -2,3,5,6-tctrahydro-l //-pyrimido[ 1,2- ]quinolines <20030L2215>. Oxidation of 2-[(2-(3,4-dihydroxiphenyl)ethyl]-l,4,5,6-tetrahydropyrimidine with MnOz gave a similar result. 

The cyclopropenium system m y combine with a large number of donor groups, mainly heterocyclic and carbocyclic systems to give cyclopropenium cyanines. En-amines or ketene acetals of appropriate basicity, e.g. Fischer Base (135) or 134, can be easily cyclopropenylated by the ethoxy cyclopropenium cation 75 as well as 2- or 4-alkylsubstituted heterocyclic quartemary salts of pyridine, quinoline, and benzothiazol in the presence of a tertiary base76,10s ... 

Ylide (364) has been obtained by heating (363) in pyridine. Isoquinoline yields a stable ylide upon reaction with ethoxycarbonylcarbene (70TL941) and the relative rates of reaction of ethoxy-carbonylcarbene with pyridine, quinoline, and acridine have been studied (88JOC4374). However, the isoquinolone (365) undergoes attack at the isoquinoline double bond to give (366). 

While the synthesis of benzofuran derivatives from suitable furan derivatives has been comparatively little investigated, the synthesis of fused two-ring and three-ring compounds containing a pyridine nucleus from furan derivatives has been more successful furo[3,2-c]pyridines (345),752>753 2,3-dihydrofuro[2,3-a ]quinolines (from 4,5-dihydro-3-furoic acid),754 acrophyllin (346), and 7-hydroxydictamnine (347) (from ethyl 2-ethoxy-4-oxo-4,5-dihydrofuran-3-carboxylate),755 are examples of compounds in this class which have been prepared. 

As already indicated, the chemistry of terminal borylene complexes is as yet almost unexplored. In addition to the photochemically induced borylene transfer, which was already discussed in Chapter 3.2, studies of the reactivity of terminal borylene complexes are restricted to two recent reports by Roper.147,148 The base-stabilized borylene complex [Os (=BNHC9H6N)Cl2(CO)(PPh3)2] (26) undergoes a reaction with ethanol to yield the ethoxy(amino)boryl complex [Os B(OEt)NHCgH6N Cl(CO) (PPh3)2] (35) according to Eq. (13) with a 1,2-shift of the quinoline nitrogen atom from the boron to the osmium center. The alcoholysis of 26 indicates that even the boron atom in base-stabilized borylene complexes displays some electrophilic character—a fact already predicted by a theoretical study.117... 

---