Synthesis and Reactions of the Novel 6‐ethyl‐4‐hydroxy‐2,5‐dioxo‐5,6‐dihydro‐2H‐pyrano[3,2‐c]quinoline‐3‐carboxaldehyde

The novel 6‐ethyl‐4‐hydroxy‐2,5‐dioxo‐5,6‐dihydro‐2H‐pyrano[3,2‐c]quinoline‐3‐carboxaldehyde ( 2 ) was efficiently synthesized from Vilsmeier–Haack formylation of 3‐(1‐ethy1‐4‐hydroxy‐2‐oxo‐(1H)‐quinolin‐3‐yl)‐3‐oxopropanoic acid ( 1 ). The aldehyde 2 was allowed to react with some nitrogen nucleophiles producing a variety of hydrazones 3 – 7 . Reaction of aldehyde 2 with hydrazine hydrate and hydroxylamine hydrochloride afforded pyrazole and isoxazole annulated pyrano[3,2‐c]quinoline‐2,5(6H)‐dione, respectively. The reactivity of aldehyde 2 was examined toward some active methylene nitrile, namely, malononitrile, ethyl cyanoacetate, and cyanoacetamide leading to 2‐iminopyrano[2′,3′:4,5]pyrano[3,2‐c]quinolines 10 – 12 , respectively. Also, some novel pyrazolo[4″,3″:5′,6′]pyrano[2′,3′:4,5]pyrano[3,2‐c]quinolines ( 13 , 14 ) and thiazolo[5″,4″:5′,6′]pyrano[2′,3′:4,5]pyrano[3,2‐c]quinolines ( 15 , 16 ) were synthesized. Structures of the new synthesized products were deduced on the basis of their analytical and spectral data.     

Synthesis of some pyrimido[4′,5′:4,5]thieno[2,3-b]quinolines and related heterocycles

Several thieno[2,3-b]quinolines 6a-i have been synthesized. These compounds were used as key intermediates in the synthesis of oxazino[4′,5′:4,5]thieno[2,3-b]quinoline 8 , pyrimido[4′,5′:4,5]-thieno[2,3-b]quinolines 9–12 , triazino[4′,5′:4,5]thieno[2,3-b] quinolines 14 and imidazo[4′,5′:4,5]-thieno[2,3-b]quinolines 17 .     

The synthesis of monomethoxynaphtho[1′,2′:4,5]thieno[2,3-c]quinolines

A series of monomethoxynaphtho[1′,2′:4,5]thieno[2,3-c]quinolines has been prepared by photocyclization of the appropriate N-methoxyphenyl-1-chloronaphtho[2,1-b]thiophene-2-carboxamides. Some of the lactams obtained were converted into the thiolactams and their S-methyl derivatives. The lactams were also converted into the corresponding 6-chloro derivatives. Some of these were catalytically dechlorinated into the monomethoxynaphtho[1′,2′:4,5]thieno[2,3-c]quinolines which were then quaternized into the N-methyl quaternary salts.     

Synthesis of 2,3‐Disubstituted Quinolines via Ketenimine or Carbodiimide Intermediates

Cyclopenta[b]quinolines and cyclohexa[b]quinolines were prepared via the reactions of α‐diazo ketones with N‐(2‐cyclopropylidenemethylphenyl)phosphanimines and N‐(2‐cyclobutylidenemethylphenyl) phosphanimine, respectively. The reaction proceeds in a cascade involving ketenimine formation, 6 π‐electron ring closure, and 1,3‐alkyl shift. A similar approach was developed for the synthesis of dihydropyrrolo‐[2,3‐b]quinolines from N‐(2‐cyclopropylidenemethylphenyl)phosphanimines and isocyanates.     

Reactions of 6‐aminopyrimidines with 2‐dimethylaminomethylenetetralone. Regiospecific Synthesis Of 5,6‐Dihydrobenzo [h]pyrimido [4,5‐b] quinolines

Benzo[h]pyrimido[4,5‐b]quinolines ( 3 ) have been synthesized via a regiospecific cyclocondensation reaction between 6‐aminopyrimidines ( 1 ) and 2‐dimethylaminomethylentetralone hydrochloride ( 2 ). The linear structure of the final compounds were determined by nmr measurements, especially by ¹H,¹H, ¹H,¹³C COSY and DEPT experiments.     

Synthesis of 10-deazariboflavin and related 2,4-Dioxopyrimido[4,5-b]quinolines

Condensation of substituted anthranilaldehydes with barbituric acid results in the formation of 2,4-dioxopyrimido[4,5-b]quinolines. Using this general synthetic approach, 7,8-dimethyl-2,4-dioxo-10-ribityl-2,3,4,10-tetrahydropyrimido[4,5-b]quinoline (10-deazariboflavin) was prepared by the condensation of barbituric acid with 4,5-dimethyl-N-ribitylanthranilaldehyde. The latter was obtained in situ by the treatment of 1-[4,5-dimethyl-N-(ribityl)anthraniloyl]-2-(p-toluenesulfonyl)hydrazine, prepared from 4,5-dimethylanthranilic acid with anhydrous sodium carbonate.     

Synthesis of some novel fused tetracyclic quinolonecarboxylic acids via 7-methyl-6,7,8,9-tetrahydro-3H-imidazo[4,5-f]quinoline and 6-methyl-5,6,7,8-tetrahydro-1H-imidazo[4,5-g]quinoline

A series of fused tetracyclic quinolonecarboxylic acids was prepared for biological evaluation. These compounds were synthesized by a route involving a regiospecific functionalization of 5-fluoro-2-methyl-1,2,3,4-tetrahydroquinoline to obtain a series of new substituted 7-methyl-6,7,8,9-tetrahydro-3H-imidazo[4,5-f]quinolines and 6-methyl-5,6,7,8-tetrahydro-1H-imidazo[4,5-g]quinolines as convenient precursors of quinolones.     

First Examples of Povarov Reaction of Cyclopentadienones

We describe herein the first examples of Povarov reaction of tetrasubstituted cyclopentadienones in the preparation of quinoline compounds. Polycyclic compounds bearing tetrahydro‐3H‐cyclopenta[c]quinoline and dihydro‐1H‐cyclopenta[c]naphtha[2,3‐h]quinoline moieties have been synthesized by one pot reaction of tetrasubstituted cyclopentadienones with N‐arylamines and formaldehyde in the presence of trifluoroacetic acid. The control of the regioselectivity was total as well with symmetrical and non symmetrical cyclopentadienones. The X‐ray structures of new quinolines were reported.     

Polycyclic N‐Heterocyclic Compounds. Part 84: Reaction of N‐(pyrido[3′,2′:4,5]thieno[3,2‐d]pyrimidin‐4‐yl)amidines or N‐(pyrido[2′,3′:4,5]furo[3,2‐d]pyrimidin‐4‐yl)amidines with Hydroxylamine Hydrochloride

The reactions of nine N‐(pyrido[3′,2′:4,5]thieno[3,2‐d]pyrimidin‐4‐yl)amidines ( 3 ) with hydroxylamine hydrochloride produced new cyclization products. These were formed via ring cleavage of the pyrimidine component followed by a 1,2,4‐oxadiazole‐forming ring closure to give N‐[2‐([1,2,4]oxadiazol‐5‐yl)thieno[2,3‐b]pyridin‐3‐yl]formamide oximes ( 11 ). Reaction of six N‐(pyrido[2′,3′:4,5]furo[3,2‐d]pyrimidin‐4‐yl)amidines ( 12 ) with hydroxylamine hydrochloride gave similar results. Effects of the newly synthesized compounds on pentosidine formation were also evaluated.     

Mannich Reaction as a New Route for the Synthesis of Tetrahydro Pyrimido Benzimidazolyl Coumarins

Condensation of coumarin‐4‐acetic acids ( 1 ) with ortho‐phenylenediamine ( 2 ) in anhydrous phosphoric acid afforded 4‐((1H‐benzo[d]imidazol‐2‐yl)methyl)‐2H‐chromen‐2‐ones ( 3 ). Attempted Mannich reaction of 3 with formalin and primary amines resulted in 4‐(2‐phenyl‐1,2,3,4‐tetrahydrobenzo[4,5]imidazo[1,2‐c]pyrimidin‐4‐yl)‐2H‐chromen‐2‐ones ( 6 ). The structures of synthesized compounds were elucidated by analyses including 2D HETCOR and DEPT experiments. Synthesized compounds have been subjected for anti‐inflammatory activity. Compound 6j exhibited promising anti‐inflammatory activity.     

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     

Synthesis and Characterization of New Heterocyclic Compounds Containing Thienylbenzo[h]Quinoline Moiety

In this paper the reaction of 2‐(2′‐thienylmethylene)‐3,4‐dihydronaphthalen‐2(1H)‐one ( 1 ) with cyanothioacetamide gave a mixture of 3‐cyano‐5,6‐dihydro‐4‐(2′‐thienyl)‐benzo[h]quinolin‐2(1H)‐thione ( 2 ) and the related disulfide 3 . Compound 2 was reacted with some halo compounds namely; ethyl chloroacetate, chloroacetamide, chloro(N‐(p‐chlorophenyl))acetamide, N¹‐chloroacetylsulfanilamide, and 2‐chloromethyl‐1H‐benzimidazole to produce a series of 2‐(substituted)methylthio‐3‐cyano‐5,6‐dihydro‐4‐(2′‐thienyl)benzo[h]quinolines 4a , 4b , 4c , 4d , 4e and 11 . Upon heating the latter compounds with sodium ethoxide, they underwent intramolecular Thorpe–Zeigler cyclization to furnish the corresponding 2‐(substituted)‐3‐amino‐5,6‐dihydro‐4‐(2′‐thienyl)‐benzo[h]thieno[2,3‐b]quinolines 5a , 5b , 5c , 5d , 5e and 12 . (3‐Cyano‐5,6‐dihydro‐4‐(2′‐thienyl)‐benzo[h]quinolin‐2‐ylthio)acethydrazide ( 8 ) and the related isomer, 3‐amino‐5,6‐dihydro‐4‐(2′‐thienyl)thieno[2,3‐b]benzo[h]quinoline‐2‐carbohydrazide ( 9 ), were also synthesized. Most of the aforementioned compounds were used as key intermediates for synthesizing other benzo[h]quinolines, benzo[h]thieno[2,3‐b]quinolines as well as benzo[h]pyrimido[4′,5′:4,5] thieno[2,3‐b]quinolines. The structure of all synthesized compounds was confirmed by spectroscopic measurements and analytical analyses.     

One‐pot Sequential Reactions Featuring a Copper‐catalyzed Amination Leading to Pyrido[2′,1′:2,3]imidazo[4,5‐c]quinolines and Dihydropyrido[2′,1′:2,3]imidazo[4,5‐c]quinolines

Tetracyclic skeletons combining an imidazo[1,2‐a]pyridine moiety with a quinoline framework such as pyrido[2′,1′:2,3]imidazo[4,5‐b]quinoline are stimulating increasing interests since they are close isosteres of a series of powerful antiproliferative compounds. In this paper, we report a novel methodology for the synthesis of pyrido[2′,1′:2,3]imidazo[4,5‐c]quinolines through one‐pot sequential reactions of commercially available or readily obtainable 2‐aminopyridines, 2‐bromophenacyl bromides, aqueous ammonia, and aldehydes. Moreover, dihydropyrido[2′,1′:2,3]imidazo[4,5‐c]quinolines could also be obtained in a similar manner by using various ketones as the substrates in place of aldehydes. Notably, the whole procedure combines condensation/amination/cyclization reactions in one pot to give complex compounds in a simple and practical manner. Compared with literature methods, the synthetic strategy reported herein has the advantages of readily available starting materials, structural diversity of products, good functional group tolerance, and obviation of step‐by‐step operations.     

Synthesis and Antimicrobial Activity of New 1,2,3‐Triazolopyrimidine Derivatives and Their Glycoside and Acyclic Nucleoside Analogs

New [1,2,4‐oxadiazolyl]methyl‐3H‐[1,2,3]triazolo[4,5‐d]pyrimidin derivatives were synthesized starting from N′‐Hydroxy‐1‐naphthimidamide. The N‐substituted acyclic nucleoside analogs as well as the substituted glycosides were also prepared by reaction with the corresponding reagents. The antimicrobial results indicated that most of the tested compounds exhibited moderate to high antimicrobial activity whereas few compounds were found to exhibit little or no activity against the tested microorganisms.     

Synthesis of N-substituted imidazo[4,5-e]benzo[1,2-c;3,4-c’]difuroxans

N-Substituted imidazo[4,5-e]benzo[1,2-c;3,4-c’]difuroxans were synthesized by phase-transfer catalyzed alkylation of imidazo[4,5-e]benzo[1,2-c;3,4-c’]difuroxan salts with various alkylating agents. Acid hydrolysis of N-(ethoxycarbonylmethyl)imidazo[4,5-e]benzo-[1,2-c;3,4-c’]difuroxans gives the corresponding carboxylic acids. Structures of the synthesized compounds were confirmed by NMR spectroscopy, high resolution mass spectrometry, IR spectroscopy, and elemental anslysis.

     

Acyliminium ion-olefin cyclization leading to isoindolo[2,1-a]quinoline derivatives

Isoindolo[2,1-a]quinolines 10 , 11 , 12 were synthesized from hydroxylactams 8 or 9 via an N-acyliminium ion-π-olefin nucleophile cyclization reaction.     

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.     

The synthesis of novel polycyclic heterocyclic ring systems via photocyclization. 23 . Naphtho[2′,1′:4,5]thieno‐[2,3‐c]naphtho[2,1‐f]quinoline

A previously unknown heterocyclic ring system, naphtho[2′,1′:4,5]thieno[2,3‐c]naphtho[2,1‐f]quinoline ( 14 ), was synthesized via oxidative photocyclization of 3‐chloro‐N‐(2‐phenanthryl)naphtho[1,2‐b]‐thiophene‐2‐carboxamide ( 9 ). Further elaboration of the lactam 10 yielded the unsubstituted ring system 14 . Structural confirmation of compound 14 was accomplished by a total assignment of its ¹H and ¹³C nmr spectra utilizing the concerted two‐dimensional nmr spectroscopic methods.     

Synthesis and application of 2‐styryl‐6,7‐dichlorothiazolo[4,5‐b]‐quinoxaline based fluorescent dyes: Part 3

A new efficient synthesis of 2‐styryl‐6,7‐dichlorothiazolo[4,5‐b]quinoxaline based fluorescent dyes was achieved by the condensation of 2‐methyl‐6,7‐dichlorothiazolo[4,5‐b]quinoxaline with selected 4‐N,N‐dialkylaminoarylaldehydes and heteroarylaldehydes in the presence of piperidine. The coloristic, fluo‐rophoric, and dyeing properties of these dyes were studied.     

The synthesis of dimethoxy- and trimethoxy[1]benzothieno[2,3-c]quinolines

Three dimethoxy[1]benzothieno[2,3-c]quinolines 24–26 were prepared by photocyclization of the appropriate 3-chloro-N-phenylbenzo[b]thiophene-2-carboxamides 15–17 to [1]benzothieno[2,3-c]quinolin-6(5H)-ones 18–20 followed by chlorination to 6-chloro[1]benzothieno[2,3-c]quinolines 21–23 and then dechlorination resulting in the title compounds. Reaction of 24–26 with methyl iodide furnished the corresponding N-methyl quaternary salts 27–29 . Sodium methoxide readily converted 21–23 to trimethoxy[1]benzothieno[2,3-c]quinolines 30–32 .