Synthesis of 1H-pyrrolo[3,2-c]quinoline derivatives via palladium-catalyzed heteroannulation of 2-aryl-3-iodo-4-(phenylamino)quinolines and 4-(N,N-allylphenylamino)-2-aryl-3-iodoquinolines

Palladium(0)/copper iodide catalyzed Sonogashira cross-coupling of 2-aryl-3-iodo-4-(phenylamino)quinolines with terminal alkynes afforded series of 1,2,4-trisubstituted 1H-pyrrolo[3,2-c]quinolines in a single-step operation. Conversely, the 4-(N,N-allylphenylamino)-2-aryl-3-iodoquinoline derivatives were found to undergo PdCl₂(PPh₃)₂/CuI catalyzed intramolecular Heck reaction to yield the corresponding 1,3,4-trisubstituted 1H-pyrrolo[3,2-c]quinolines.     

Perhydrofuro[3,2-<Emphasis Type="Italic">c</Emphasis>]-, perhydropyrano[3,2-<Emphasis Type="Italic">c</Emphasis>]-, and 4-ethoxy-2-(5-R-furan-2-yl)tetrahydroquinolines. Synthesis and transformations

Partly hydrogenated 2-[5-methyl(bromo, nitro)furan-2-yl]-substituted furo[3,2-c]quinolines, pyrano-[3,2-c]quinolines, and 4-ethoxyquinolines were synthesized by the imino Diels-Alder (Povarov) reaction. Cycloadditions of these compounds with maleic, citraconic, and dibromomaleic anhydrides, as well as with acryloyl, methacryloyl, and cinnamoyl chlorides led to the formation of substituted epoxyisoindolo[2,1-a]-quinolines and -quinolinecarboxylic acids. Oxidation of the double C=C bond in the adducts, esterification of the carboxy group, and aromatization of the 7-oxabicycloheptene fragment were accomplished.     

One-pot synthesis of 2-substituted furo[3,2-c]quinolines via tandem coupling-cyclization under Pd/C-copper catalysis

Pd/C-Cu catalyzed coupling reactions of 3-iodo-1H-quinolin-4-ones with a variety of terminal alkynes afforded furo[3,2-c]quinolines regioselectively in good to excellent yields. 3-Alkynyl quinolones were isolated under the same reaction conditions when the nitrogen of 3-iodo-1H-quinolin-4-one was substituted with an alkyl group.     

Synthesis of 2-bromomethyl-4-methyl-2,3-dihydrofuro[3,2-<Emphasis Type="Italic">c</Emphasis>]-quinoline and some its transformations

Electrophilic intramolecular heterocyclization of 3-(2-chloroprop-2-en-1-yl)-2-methylquinolin-4-ol by the action of bromine gave 2-bromomethyl-2-chloro-4-methyl-2,3-dihydrofuro[3,2-c]quinoline hydrobromide which was converted into 2-hydroxymethyl-, 2-alkoxymethyl-, and 2-dialkylaminomethyl-4-methylfuro[3,2-c]quinolines by treatment with the corresponding nucleophiles.     

Benzo[b]Furan in the Povarov Reaction

The Povarov-type condensation of ethyl 2-(arylimino)acetates, 1-aryl-2-aryliminoethanones or N-benzylideneanilines with benzo[b]-furan affords 5,6,6a,11b-tetrahydrobenzofuro[2,3-c]quinolines and/or related benzofuro[2,3-c]quinolines.     

Synthesis of substituted 2,4-dimethylthieno[3,2-<Emphasis Type="Italic">c</Emphasis>]quinolines

A procedure was developed for the synthesis of substituted 2,4-dimethylthieno[3,2-c]quinolines via intramolecular cyclization and subsequent aromatization of 3-(2-chloroprop-2-en-1-yl)-and 3-(2-oxopropyl)-2-methylquinoline-4-thiols. The latter were obtained by alkaline hydrolysis of the corresponding thiuronium salts which were prepared in turn by reactions of 4-chloro-3-(2-chloroprop-2-en-1-yl)-and 4-chloro-3-(2-oxopropyl)-2-methylquinolines with thiourea.     

New synthetic approach to epoxyisoindolo[2,1-a]quinolines based on cycloaddition reactions of 2-furyl-substituted tetrahydroquinolines with maleic anhydride and acryloyl chloride

A procedure was developed for the synthesis of hydrogenated furyl-substituted furo[3,2-c]quinolines, pyrano[3,2-c]quinolines, and 4-ethoxy-and 4-(2-oxopyrrolidin-1-yl)quinolines. The reactions of these compounds with acryloyl chloride and maleic anhydride produce epoxyisoindolo[2,1-a]quinoline derivatives through successive acylation at the quinoline nitrogen atom and intramolecular exo-[4+2]-cycloaddition at the furan moiety. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1023–1038, May, 2007.     

Fused 1,2,4-triazole heterocycles. IV. Synthesis of four new heterocyclic ring systems of [1,2,4]triazolo[1,3]thiazinoquinolines

Syntheses of 5H-[1,2,4]triazolo[5′,1′:2,3][1,3]thiazino[5,4-c]quinolines 8, 5H-[1,2,4]triazolo[3′,4′:2)3][1,3]thiazino[5,4-c]quinolines 9, 5H-[1,2,4]triazolo[5′,1′:2,3][1,3]thiazino[5,6-c]quinolines 14 and 5H-[1,2,4]triazolo[3′,4′:2,3][1,3]thiazino[5,6-c]quinolines 15 are described starting from 4-chloro-3-chloromethylquinaldine (4) and 1,2,4-triazole-5-thiols 5 taking advantage of different reactivity of the chlorine atoms of 4 under different reaction conditions. The structures of products 8, 9, 14 and 15 and the intermediates leading to them were confirmed by desulfurization, unequivocal syntheses and nmr spectroscopy as well.     

Skeletal Wagner-Meerwein rearrangement of perhydro-3a,6;4,5-diepoxyisoindoles

An investigation of a skeletal Wagner-Meerwein rearrangement of variously substituted or quinoline-annulated 3a,6;4,5-diepoxyisoindol-1-ones is reported. Optimum reaction conditions (Ac₂O, BF₃·OEt₂, rt) were discovered for the formation of the target 4,6-epoxycyclopenta[c]pyridines in 40-80% yields. It was shown that the direction of the sigmatropic rearrangement of 3a,6;4,5-diepoxyisoindol-1-ones depended dramatically on the carboxyl group position (exo-/endo-) in the oxabicyclo[2.2.1]heptane moiety. The spatial structure of previously unknown 7,9-epoxycyclopenta[4,5]pyrido[1,2-a]quinolines derived from Wagner-Meerwein rearrangement of 2,11b-epoxyoxireno[6,7]isoindolo[2,1-a]quinolines was established based on the X-ray analysis data. The skeletal rearrangement proceeded regio- and stereospecifically in all the cases examined due to the absence of the epimerization of the carbon atoms adjacent to the carbocation centres.     

Reactions of 4-Aryl-2-hydrazino-3-nitro-6-R-quinolines with HNO2

The reaction of 4-aryl-2-hydrazino-3-nitro-6-R-quinolines with NaNO₂ in AcOH gives the corresponding tetrazolo[1,5-a]quinolines. In contrast to tetrazolo[1,5-c]pyrimidines they cannot be converted to 6-R-4-phenyl[1,2,5]oxadiazolo[3,4-b]quinoline-3-oxides by heating in THF, toluene, or AcOH. Total energy quantum-chemical calculations using the MINDO/3 and MNDO methods show that [1,2,5]oxadiazolo[3,4-b]quinoline-3-oxides are significantly higher in energy (230-280 kcal/mol) than the mentioned tetrazolo[1,5-a]quinolines and hence their formation is unlikely.     

The synthesis of substituted [1]benzothieno[2,3-c]quinolines and their N-methyl quaternary salts

Four substituted [1]benzothieno[2,3-c]quinolines 14a-14d were prepared by photocyclization of the appropriate carboxamides 8a-8d to the corresponding [1]benzothieno[2,3-c]quinolin-6(5H)-ones 12a-12d followed by chlorination to 6-chloro[1]benzothieno[2,3-c]quinolines 13a-13d and dechlorination resulting in the title compounds. Treatment of 14a-14d with iodomethane furnished the corresponding N-methyl quaternary salts 5a-5d .     

A convenient synthesis of benzofuro[3,2-c]isoquinolines and naphtho[1′,2′:4,5]furo[3,2-c]isoquinolines

A convenient method for the preparation of benzofuro[3,2-c]isoquinoline derivatives is described. The condensation reaction of methyl 2-(chloromethyl)-benzoate with substituted salicylonitriles 7a-c and intramolecular cyclization of the resulting substituted methyl 2-[(2-cyanobenzyl)oxy]benzoates 10a-c using potassium tert-butoxide results in the substituted benzofuro[3,2-c]isoquinolin-5(6H)-ones 1a-c. The same sequence of reactions starting from 2-(chloromethyl)benzonitrile and compounds 7a-c gave substituted 5-aminobenzofuro[3,2-c]isoquinolines 13a-c. In addition, this method is useful for the synthesis of other heterocycles. For example, using 1-cyano-2-naphthol 16, instead of the salicylonitriles 7a-c, gives naphtho[1′,2′:4,5]furo[3,2-c]isoquinolines.     

Synthesis and cycloaddition reactions of ethyl glyoxylate imines. Synthesis of substituted furo-[3,2-c]quinolines and 7H-indeno[2,1-c]quinolines

Lewis acid catalyzed cycloaddition reactions of ethyl glyoxylate imines to dihydrofuran and indene yield substituted hexahydrofuro[3,2-c]- and tetrahydro-7H-indeno[2,1-c]quinolines respectively. Oxidation of the adducts with 2,3-dichloro-5,6-dicyanobenzoquinone affords the corresponding aromatic compounds.     

Five-membered 2,3-dioxo heterocycles: CI. Reaction of 3-aroylpyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones with arylhydrazines. Crystal and molecular structure of substituted 2-hydrazonopyrrolo[2,1-c][1,4]benzoxazine

A new direction of nucleophilic attack was revealed in the reactions of 3-aroylpyrrolo[2,1-c][1,4]-benzoxazine-1,2,4-triones with o-tolylhydrazine and 2-hydrazinylbenzoic acid hydrochloride, which afforded the corresponding hydrazones at the C²=O carbonyl group, substituted 2-(2-o-tolylhydrazono)pyrrolo[2,1-c]-[1,4]benzoxazine-1,4(2H)-diones and pyrrolo[2,1-c][1,4]benzoxazin-2(4H)-ylidenehydrazinylbenzoic acids. The structure of (Z)-2-{2-[3-benzoyl-1,4-dioxo-1H-pyrrolo[2,1-c][1,4]benzoxazin-2(4H)-ylidene]hydrazinyl}-benzoic acid was determined by X-ray analysis.     

The synthesis of monomethoxy[1]benzothieno[2,3-c]quinolines

A series of monomethoxy[1]benzothieno[2,3-c]quinolines 24-28 were prepared by photocylization of the appropriate 3-chloro-N-phenylbenzo[b]thiophene-2-carboxamides 9–13 to [1]benzothieno[2,3-c]quinolin-6(5H)-ones 14-18 followed by chlorination to 6-chloro[1]benzothieno[2,3-c]quinolines 19-23 then dechlorination resulting in the title compounds except for 25 which was achieved by direct reduction of 15 . Reaction of 24-28 with methyl iodide provided the corresponding N-methyl quaternary salts 29-33 . Also, conversion of 4-meth-oxy[1]benzothieno[2,3-c]quinolin-6(5H)-one 16 to 4-methoxy-6-methylthio[1]benzothieno[2,3-c]quinoline 35 and 4,6-dimethoxy[1]benzothieno[2,3-c]quinoline 36 is described.     

Synthesis of 4-alkyl(aryl,hetaryl)-2-thioxo-5,6,7,8-tetrahydroquinoline-3-carbonitriles and their derivatives by cross-recyclization of 4-alkyl(aryl,hetaryl)-2,6-diamino-4<Emphasis Type="Italic">H</Emphasis>-thiopyran-3,5-dicarbonitriles with 4-(cyclohex-1-en-1-yl)-morpholine,alkyl halides,and cyclohexanone

Cross recyclization of 4-substituted 2,6-diamino-4H-thiopyran-3,5-dicarbonitriles with 4-(cyclohex-1-en-1-yl)morpholine, alkyl halides, and cyclohexanone gave the corresponding substituted 2-thioxo-1,2,5,6,7,8-hexahydroquinoline-3-carbonitriles, 2-alkylsulfanyl-5,6,7,8-tetrahydroquinoline-3-carbonitriles, 3-amino-5,6,7,8-tetrahydrothieno[2,3-b]quinoline-2-carboxamides, and 4-oxo-2,2-pentamethylene-1,2,3,4,7,8,9,10-octahydropyrimido[4′,5′:4,5]thieno[2,3-b]quinolines. The structure of 3-(4-bromophenyl)-2,2-pentamethylene-11-(2-thienyl)-1,2,3,4,7,8,9,10-octahydropyrimido[4′,5′:4,5]thieno[2,3-b]quinoline was proved by X-ray analysis.     

Synthesis and spectral properties of substituted 4-chlorooxazoloquinolines

Summary The treatment of a mixture of linearly and angularly annelated 2-substituted oxazolo[4,5-f]quinolones (5a–c) and oxazolo[5,4-g]quinolones (6a–c) and similarly the treatment of 2-substituted oxazolo[5,4-f]quinolones (7a–c) and oxazolo[4,5-g]quinolones (8b,c) with POCl₃ afforded substituted 4-chlorooxazolo[4,5-f]quinolines (9a–c) and 2-substituted 4-chlorooxazolo[5,4-f]quinolines (10b,c), respectively. Spectral characteristics of the synthesized derivatives (¹H and¹³C NMR, IR, UV, and MS) are discussed.Dedicated to Prof.Fritz Sauter on the occasion of his 65th birthday     

Structural analogues of quinoline alkaloids: Straightforward route to [1,3]dioxolo[4,5-c]quinolines with antibacterial properties

Compounds bearing [1,3]dioxolo-quinoline scaffolds have been found in quinoline-based natural products; the only exception is the [1,3]dioxolo[4,5-c]quinoline moiety with a rare occurrence in both natural and synthetic derivatives. In this article, we report the preparation of diversely substituted and functionalized [1,3]dioxolo[4,5-c]quinolines using [1,3]dioxolo[4,5-c]quinoline-4-carbaldehyde (DQC) as the common intermediate. DQC was synthesized on a large scale from anthranilic acid and chloroacetone as the starting materials, with the rearrangement of acetonyl-anthranilate as the key step. The developed method allows for the simple preparation of [1,3]dioxolo[4,5-c]quinolines with various C2 substituents on the quinoline scaffold. Additionally, the synthetic route was successfully applied to the preparation of 3-hydroxyquinoline-4(1H)-ones. The target compounds were tested against representative Gram-positive/negative bacteria, and two derivatives exhibited submicromolar minimum inhibitory concentrations against Micrococcus luteus.     

Synthesis of 4b,5,10a,11-tetrahydroindeno[1,2-b]quinolin-10-ones from Baylis-Hillman adducts

We developed an efficient synthetic method for indenoquinoline skeletons from Baylis-Hillman adducts. 4b,5,10a,11-Tetrahydroindeno[1,2-b]quinolin-10-ones and 7H-indeno[2,1-c]quinolines were prepared from Baylis-Hillman adducts in polyphosphoric acid.     

Synthesis of furo[2,3-c]-2,7-naphthyridine derivatives via domino heterocyclization reaction

2-Amino-4-cyanomethyl-6-dialkylamino-3,5-pyridinedicarbonitriles were found to react with substituted oxiranes yielding 5,6-diamino-8-dialkylamino-1,2-dihydrofuro[2,3-c]-2,7-naphthyridine-9-carbonitriles. The oxirane ring was shown to be opened selectively from the unsubstituted side and further cyclization occurred with participation of 3-CN, but not 5-CN of the starting pyridines. The furonaphthyridines obtained were converted into 2-dialkylamino-5-methyl-9,10-dihydro-4H-furo[2,3-c]pyrimido[4,5,6-ij]-2,7-naphthyridine-1-carbonitriles and 2-dialkylamino-5,6,9,10-tetrahydro-4H-spiro{furo[2,3-c]pyrimido[4,5,6-ij]-2,7-naphthyridine-5,1′-cyclohexane}-1-carbonitriles by treatment with acetic anhydride and cyclohexanone, respectively. The structure of prepared compounds was confirmed unambiguously by X-ray crystallographic study.