New fused pyrazines. Synthesis of pyrido[3′,2′:4,5]‐thieno[2,3‐e]pyrrolo[1,2‐a]pyrazine derivatives

The synthesis of the title compounds was achieved using the key intermediate ethyl 4,6‐dimethyl‐3‐(pyrrol‐1‐yl)thieno[2,3‐b]pyridine‐2‐ carboxylate 2. This latter compound was obtained via the interaction of the thienopyridine amino ester 1 with 2,5 dimethoxytetrahydrofuran in acidic medium.     

Syntheses of some new azolopyrido‐[4′,3′:4,5]thieno[2,3‐d]pyrimidines

Diethyl 2‐[(ethoxythioxomethyl)amino]‐4,5,6,7‐tetrahydrothieno[2,3‐c]‐pyridine‐3,6‐dicarboxylate 2 , prepared from diethyl 2‐isothiocyanato‐4,5,6,7‐tetrahydrothieno[2,3‐c]pyridine‐3,6‐dicarboxylate 1 by boiling in anhydrous ethanol, was converted into pyrido[4′,3′:4,5]thieno[2,3‐d]pyrimidine derivatives 3, 4 by treatment with hydrazine hydrate. The tetracyclic systems imidazo[1,2‐a]pyrido‐[4′,3′:4,5]thieno[2,3‐d]pyrimidine 9 and pyrido[4′,3′:4,5]thieno[2,3‐d][1,3]thiazolo‐[3,2‐a]pyrimidine 10 were synthesized by the reaction of 2 with 1,2‐diaminoethane and aminoethanethiol, respectively. The hydrazino derivative 4 underwent cyclization reactions with orthoesters and nitrous acid to give the corresponding pyrido[4′,3′:4,5]thieno[2,3‐d][1,2,4]triazolo[1,5‐a]pyrimidines 5, 6 and pyrido[4′,3′:4,5]thieno[3,2‐e][1,2,3,4]tetrazolo[1,5‐a]pyrimidine 8 , respectively. Moreover, reactions of 3 with cyanogen bromide, N‐carbethoxyhydrazine, carbon disulfide, and ethylchloroformate resulted in the formation of the new pyrido[4′,3′:4,5]thieno[2,3‐d][1,3,4]thiadiazolo[3,2‐a]pyrimidine derivatives 12–15 . © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:280–286, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10030     

Ring closure reactions of pyrido[2,3‐d]pyrimidines to pyrano[2′,3′:4,5]‐ and oxazolo[5′,4′:4,5]pyrido[2,3‐d]pyrimidines

The cyclocondensation of 5‐hydroxy‐pyrido[2,3‐d]pyrimidines 1 with malonates gives pyrano[2′,3′:4,5]‐pyrido[2,3‐d]pyrimidines 2 . Nitration of 1 and reduction with zinc in the presence of carboxylic acids/anhydrides gave 2‐alkyloxazolo[5′,4′:4,5]pyrido[2,3‐d]pyrimidines 4 , which were ring‐opened to 6‐aminopyrido[2,3‐d]pyrimidines 5, 6 and 7 . Cyclization of 6‐aminopyrido[2,3‐d]pyrimidines 6 with benzoylchlorides 8 gave 2‐aryloxazolo[5′,4′:4,5]pyrido[2,3‐d]pyrimidines 9 . Reaction conditions for the cyclization have been studied by differential scanning calorimetry (DSC).     

Reactions of hydrazonoyl halides 43 : Synthesis of some new 2,3‐dihydro‐1,3,4‐thiadiazoles,pyrazoles, pyrazolo[3,4‐d]‐pyridazines,thieno[2,3‐b]pyridines,pyrimidino[4′,5′:4,5]thieno[2,3‐b]‐pyridines and pyrrolo[3,4‐d]pyrazoles

2,3‐Dihydro‐1,3,4‐thiadiazoles, pyrazoles, pyrazolo[3,4‐d]pyridazines, thieno[2,3‐b]pyridines, pyrim‐idino[4′,5′:4,5]thieno[2,3‐b]pyridines and pyrrolo[3,4‐d]pyrazoles were obtained in a good yields by treatment of hydrazonoyl halides with each of alkyl carbodithioates, 3‐(dimethylamino)‐1‐naphtho[1,2‐d]furan‐2‐ylprop‐2‐en‐1‐one and N‐arylmalemides.     

Synthesis of 7,8,9,10-tetrahydropyrido[3′,4′:4,5]pyrrolo[2,3-c]quinolines

A series of structurally novel 7,8,9,10-tetrahydropyrido[3′,4′:4,5]pyrrolo[2,3-c,]quinolines, 4a-c , were synthesized via a facile Fischer indole cyclization from the appropriately substituted hydrazinoquinolines 2a-c . Acetamides 4a,c were hydrolyzed to 5a,b and further converted to tertiary amines 6a-c . Potent antihypertensive activity has been observed with a number of the title compounds as well as the intermediate 3a .     

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.     

Syntheses of substituted pyrazolo[3,4-b]quinolines, 3,4-dihydro-4-oxopyrimido[4′,5′:4,5]theino[2,3-b]quinoline and pyrido[1′,2′:1,2]pyrimido[4,5-b]quinoline

Syntheses of substituted pyrazolo[3,4-b]quinolines, 3,4-dihydro-4-oxopyriraido[4′,5′:4,5]theino[2,3-b]quinoline and 12-phenylpyrido[1′,2′:1,2[pyrimido[4,5-b]quinoline are described.     

Synthesis of pyrido[1′,2′:1,2]imidazo[4,5-b]pyrazines from 2,3-dichloro-5,6-dicyanopyrazine with 2-aminopyridines

Novel synthesis of the title compounds by the facile cyclization between 2,3-dichloro-5,6-dicyanopyrazine and various 2-aminopyridines under relatively mild conditions is described. The reactivity depended on the basicity of 2-aminopyridines.     

Synthesis and Reactions of Naphtho[1′,2′:4,5]Furo[3,2‐b]Pyridine and Naphtho[1′,2′:4,5]Furo[3,2‐d]Pyrimidine Derivatives

2‐Acyl‐3‐aminonaphtho[2,1‐b]furan ( 1 ) reacts with activated methylene such as malono nitrile or ethyl cyanoacetate to afford naphtho[1′,2′:4,5]furo[3,2‐b]pyridine 2a,b . Chloroacylation of the amino group in compound ( 1 ) gave compound 3 which reacts with different amines to produce compound 4 .     

Synthesis and total 1H-NMR assignment of naphtho[1′,2′:4,5]thieno[2,3-c][1,10]phenanthroline and naphtho[2′,1′:4,5]-thieno[2,3-c] [1,10]phenanthroline

Naphtho[1′,2′:4,5]thieno[2,3-c][1,10]phenanthroline and naphtho[2′,1′:4,5]thieno[2,3-c][1,10]phenanthroline, two novel polycyclic heterocyclic ring systems, have been synthesized in four steps from known starting materials. The total ¹H nmr spectral assignments were made using a COSY experiment to identify the spin systems.     

Synthesis,structure and some reactions of 4a',5′,6′,7′,8′,8a'‐hexahydro‐4′H‐spiro[cyclohexane‐1,9′‐[1,2,4]triazolo[5,1‐b]‐quinazolines]

2′‐Substituted 5′,6′,7′,8′‐tetrahydro‐4′H‐spiro[cyclohexane‐1,9′‐[1,2,4]triazolo[5,1‐b]quinazolines] 3a‐d were synthesized by condensation of 3‐substituted 5‐amino‐1,2,4‐triazoles 1a‐d with 2‐cyclohexylidene cyclohexanone 2 in DMF. The compounds 3 were hydrogenated with sodium borohydride in ethanol to give 2′‐substituted cis‐4a',5′,6′,7′,8′,8a'‐hexahydro‐4′H‐spiro[cyclohexane‐1,9′‐[1,2,4]triazolo[5,1‐b]quinazolines] 4a‐d in high yields. The reactions of alkylation, acylation and sulfonylation of the compounds 4 were studied. The structure of the synthesized compounds was determined on the basis of NMR measurements including HSQC, HMBC, NOESY techniques and confirmed by the X‐ray analysis of 6 and 11b . The described synthetic protocols provide rapid access to novel and diversely substituted hydrogenated [1,2,4]triazolo[5,1‐b]quinazolines.     

Pyrido[2′1′:2,3]imidazo[4,5-c]isoquinoline and the alkylation of pyrido[2′,1′:2,3]imidazo[4,5-c]isoquinolin-5(6H)-one

The reaction of 2-aminopyridine, o-phthaldehydic acid and potassium cyanide gave pyrido[2′,1′:2,3]imidazo[4,5-c]isoquinolin-5(6H)-one, which upon treatment with propargylbromide, yielded both O and N alkylated products. 2-Aminopyridine, o-phthaldehyde and potassium cyanide gave 1-cyano-2-(2-pyridyl)isoindole which rearranged in acid to give the previously unreported parent pyrido[2′,1′:2,3]imidazo[4,5-c]isoquinole. Structures were confirmed using uv, ir, nmr and x-ray spectroscopy.     

Synthesis of 1,2,3,4,4a,5-hexahydropyrido[1′,2′:4,5][1,4]oxazino[2,3-b]quinoxaline derivatives

Reactions of 2,3-dichloroquinoxalines with 2-(hydroxymethyl)piperidine resulted in a series of 1,2,3,4,4a,5-hexahydropyrido[1′,2′:4,5][1,4]oxazino[2,3-b]quinoxaline derivatives. The structures of the products were confirmed by nmr and x-ray crystallography.     

Synthesis of new heteroaromatic nitrogen ligands: Pyrimido‐[4″,5″:4′,5′]‐thieno[3′,2′:4,5]thieno[3,2‐d]pyrimidines and 1,2,3‐triazine[4″,5″:4′,5′]thieno[3′,2′:4,5]thieno[3,2‐d]‐1,2,3‐triazines

An efficient one‐pot access for the synthesis of the previously unreported tetracyclic fused pyrimido‐[4″,5″:4′,5′]thieno[3′,2′:4,5]thieno[3,2‐d]pyrimidine ( 3 ) and 1,2,3‐triazine[4″,5″:4′,5′]thieno‐[3′,2′:4,5]thieno‐[3,2‐d]‐1,2,3‐triazine ( 5 ) heteroaromatic nitrogen ligands is described. The title compounds 3 and 5 were obtained from 3,4‐diaminothieno[2,3‐b]thiophene‐2,5‐dicarbonitrile and phosgeniminium chloride and sodium nitrite/HCl, respectively. Substituted condensed thieno[2,3‐b]thiophene derivatives 4 and 6 were synthesized by nucleophilic displacement of the chloroderivatives 3 and 5 .     

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.     

Compounds in the pyrrolo[3′,4′:4,5] pyrrolo[3,4-b]indole series

Compounds in the new pyrrolo[3′,4′:4,5]pyrrolo[3,4-b]indole series have been produced by an imide cyclization of appropriate derivatives of pyrrolo[3,4-b]indole.     

Tricyclic heterocyclic systems: Pyrazolo[5′,4′:4,5]-and pyrazolo-[3′,4′:4,5]pyrano[2,3-b]pyridine derivatives

By reacting 2-chloronicotinoyl chloride with acetyl or benzoyl acetate, ethyl 2-methyl- or 2-phenyl-4-oxopyrano[2,3-b]pyridine-3-carboxylates were prepared. The nucleophilic rearrangement of the latter with hydrazines gave rise to the title compounds.     

Synthesis of New Furo[2,3‐d]pyrimidines and Pyrimido[4′,5′:4,5]furo[2,3‐d]pyrimidines

Sodium salt of 4‐hydroxy‐6‐methyl‐2‐phenylpyrimidine‐5‐carbonitrile ( 3 ) was subjected to alkylation with different a‐halo compounds, where the corresponding O‐alkylated products 4_a‐g were obtained. Ring closure of the O‐alkylated product 4_a‐c performed using sodium ethoxide in refluxing ethanol afforded furo[2,3‐d]pyrimidines 5_a‐c The latter compounds on reaction with a variety of reagents gave other new furopyrimidines as well as a number of furodipyrimidines.