Some derivatives of pyrimido [5,4-b]quinoline

10-Chloro-2,4-dioxo derivatives of pyrimido[5,4-b]quinoline have been synthesized, and nucleophilic substitution reactions in these compounds have been studied.     

Novel synthesis of isoxazolo[5,4-b]quinolines

Isoxazolo[5,4-b]quinolines have been prepared by reacting 3-acyl or aroyl-2-chloro-6-alkoxy or 6,7-dialkoxyquinolines with hydroxylamine. The method is of general applicability for obtaining this class of compounds and involves the use of easily available starting materials.     

Synthesis of 3-oxoisothiazolo[5,4-b] pyridines

3-Oxoisothiazolo[5,4-b]pyridines were synthesized for the first time by the reaction of 3-cyanopyridine-2-thiones or bis(3-cyanopyridyl) disulfides with concentrated sulfuric acid. It is demonstrated that 3-carbamoylpyridine-2-thiones are formed as intermediates. The 3-oxoisothiazolopyridines were converted to 3-bromoisothiazolopyridines and pyridine-2-thiones. The bromination of pyridine-2-thione was studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 508–512, April, 1982.     

Study of the nucleophilic substitution reactions of 2,4,10-trichloropyrimido[5,4-b]quinoline

A number of pyrimido[5,4-b]quinoline derivatives were synthesized. It is shown that in the reaction of 2,4,10-trichloropyrimido[5,4-b]quinoline (II) with strong nucleophilic reagents (OCH₃ and SH) both of the halogens of the pyrimidine ring are replaced, while with amines substitution of the halogens of the pyrimidine ring proceeds successively; under more severe conditions, all three halogen atoms of II are replaced by amine residues.     

New derivatives of 3-methylisoxazolo[5,4-b]pyridine

The synthesis and properties of 4,6-dichloro- (IV), 4-chloro- (XII) and 6-chloro-3-methyl-isoxazolo[5,4-b]pyridine (XI) are described. Depending on the reaction conditions compound IV with hydrazine or methoxide gave mono- or bi-substituted products. The halogen atom at the 4-position was shown to be the more mobile.     

Synthesis of 2-substituted 3-oxoisothiazolo[5,4-b]pyridines

Starting with 2-chloro-3-pyridinecarboxylic acid 1 , three different routes to prepare 3-oxoisothiazolo-[4,5-b]pyridines 10 were studied.     

An alternative synthesis of 10H-indolo[3,2-b]quinoline and its selective N-alkylation

A new and a more efficient synthesis of 10H-Indolo[3,2-b]quinoline (quindoline) is reported. The synthesis involved N-arylation of 3-aminoquinoline with triphenylbismuth diacetate followed by oxidative cyclization using paOadium(II) acetate. A selective N-alkylation methodology for quindoline was also developed. Alkylation on N-5 was obtained in sulpholane, while alkylation on N-10 was achieved in acetone in the presence of potassium hydroxide. A sequential N-5- and N-10 double alkylation procedure was also formulated.     

An efficient synthesis of pyrazolo[3,4-b]quinolin-3-amine and benzo[b][1,8]naphthyridine derivatives

2-Oxo-4-phenyl-1,2,5,6,7,8-hexahydroquinoline-3-carbonitrile (10) reacted with hydrazine hydrate, phenylisothiocyanate or benzoyl chloride to give derivatives 12, 13 and 15, respectively. The latter two products were treated with hydrazine hydrate to afford pyrozole[3,4-b]quinolines derivatives 14 and 16, respectively. Compound 10 also reacted with acetonitrile dimer or malononitrile dimer to yield benzo[b][1,8]-naphthyridine derivatives. A single crystal X-ray crystallographic analysis was performed on compound 10, confirming its structure.     

The synthesis of benzofuroquinolines. I. Some benzofuro[2,3-b]quinoline and benzofuro[3,2-c]quinoline derivatives

Benzofuro[2,3-b]quinoline ( Ia ) and its 11-methyl derivative ( Ib ) were synthesized by demethylcyclization of 3-(o-methoxyphenyl)-1,2-dihydroquinolin-2-ones (VIa,b). Benzofuro[2,3-b]quinoline-11-carboxylic acid (Id) was synthesized by chlorination followed by the action of potassium hydroxide of a lactone (IX) prepared by demethyl-cyclization of 3-(o-methoxyphenyl)-2-oxo-1,2-dihydroquinoline-4-carboxylic acid (VIII). Isomeric benzofuro[3,2-c]quinoline (Ha) and its 6-methyl derivative (IIb) were synthesized by demethyl-cyclization of 3-(o-methoxyphenyl)-1,4-dihydroquinolin-4-ones (XIa,b). Both the methyl derivatives (Ib and IIb) were converted to the carboxylic acids (Id and IId) through condensation with benzaldehyde followed by oxidation. The benzofuroquinolines (Ia,b,d and IIa,b) thus obtained were oxidized to the corresponding N-oxides (IIIa,b,d and IVa,b).     

Synthesis of 3-aryl-6H-isoxazolo[3,4-d]pyrazolo[3,4-b]pyridines and 3-aryl-6H-isoxazolo[5,4-d]pyrazolo[3,4-b]pyridines

The synthesis and characterization of a number of 3-aryl-6H-isoxazolo[3,4-d]pyrazolo[3,4-b]pyridines and 3-aryl-6H-isoxazolo[5,4-d]pyrazolo[3,4–6]pyridines from common precursors, 5-benzoyl-4-chloro-1H-pyrazolo-[3,4-b]pyridines, has been described. The structures were determined by unambiguous chemical synthesis and by isolation and ¹³C nmr analysis of some key, isolated, intermediates. The ability of these compounds to displace [3H]flunitrazepam from CNS binding sites was also observed.     

Isothiazolo[5,4-b]pyridine analogs of nalidixic acid

The synthesis and antibacterial evaluation of a number of isothiazolo[5,4-b]pyridine isosteres of nalidixic acid are described.     

A facile synthesis of 2-aminothiazolo[5,4-b]- and 2-aminothiazolo[4,5-c] pyridines

The hydrochlorides of the title compounds are obtained in moderate yields by refluxing 2-chloro-3-aminopyridine or 3-amino-4-chloropyridine, respectively, with an alkyl. Aralkyl-, or aryl isothiocyanate in absolute ethanol solution. A proof is presented that the 2-aminothiazolopyridine hydrochloride and not the isomeric o-chloropyridylthiourea is the product of this reaction. The free-bases may be obtained from the hydrochlorides with aqueous sodium bicarbonate. A mechanism for the formation of the thiazole ring is briefly considered. The interactions of 2-chloro-3-aminopyridine with l-substituted-5-mereapto-1H-tetrazoles are also described.     

Synthesis of thiazolo[5,4-b]pyridine-2-carboxamides

A convenient procedure was developed for preparation of thiazolo[5,4-b]pyridine-2-carboxamides by oxidation of monothiooxamides synthesized from 3-aminopyridine.     

Synthesis of new dihydrooxathiino[2,3-b]quinoline

A synthesis of new dihydrooxathiinoquinoline 4 is described. The key compound 6 was prepared by known methods from acetoacetanilide 1 . A condensation of β-chlorosulfide 6 in 75% aqueous sulfuric acid gave quinolone 5 . Conversion of 5 to 4 was achieved by treatment with potassium hydroxide in ethanol solution.     

异色满并[4,3-b]喹啉衍生物的合成

早在1931年,Hetherington等从念珠状曲菌(Aspergillus Cand inin)和土曲菌(Asperillus tereus)等菌类中分离出带有异色满(Isochroman)环系结构的左旋抗菌素橘霉素(C itrinin),后来又相继发现诸多带有异色满环系的天然产物[1-3],新近在软木木质素中也发现了多种具有异色满结构的     

An unusual arylation of 4-oxo-3,4-dihydropyrimido[4,5-b]quinoline

Treatment of 4-oxo-3,4-dihydropyrimido[4,5-6 ]quinoline (II) with phosphorus oxychloride and a dialkylaniline resulted in the introduction of a p-dialkylaminophenyl group at position-5, and reduction of the central (pyridine) ring, as well as substitution of oxygen by chlorine at po-sition-4, forming compounds considered to be 4-chloro-5-(p-dialkylaminophenyl)-5, 10-dihydro-pyrimido[4,5-6 ]quinolines (XV). Several 4-oxo-3,4-dihydropyrimido[4,5-b ]quinolines having phenyl substituents at position-5 were synthesized unequivocally, and could be readily reduced to the corresponding 4-oxo-5-phenyl-3,4,5,10-tetrahydropyrimido[4,5-6]quinolines, and the 4-oxo group replaced by chlorine, in the usual manner, leading to compounds related structurally to XV. Comparison of the chemical and physical properties of these compounds established the structure of XV, and a mechanism which rationalizes the formation of XV from II is presented.