Synthesis of 3‐substituted pyrido[4′,3′:4,5]thieno[2,3‐d]pyrimidines and related fused thiazolo derivatives

Convenient syntheses of 3‐substituted ethyl 4‐oxo‐2‐thioxo‐1,2,3,4,5,6,7,8‐octahydropyrid[4′,3′:4,5]thieno[2,3‐d]pyrimidine‐7‐carboxylates 3a, b, 6, 11–13 , ethyl 3‐methyl‐5‐oxo‐2,3,6,9‐tetrahydro‐5 H‐pyrido[4′,3′:4,5]thieno[2,3‐d][1,3]thiazolo[3,2‐a]pyrimidine‐8‐7H‐carboxylate ( 4 ), and ethyl 2‐methyl‐5‐oxo‐2,3,6,9‐tetrahydro‐5H‐pyrido[4′,3′:4,5]thieno[2, 3‐d][1,3]thiazolo[3,2‐a]pyrimidine‐8[7H]carboxylate ( 8 ) from diethyl 2‐isothiocyanato‐4,5,6,7‐tetrahythieno[2,3‐c]pyridine‐3,6‐dicarboxylate ( 1 ) are reported. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:201–207, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10131     

Synthesis of pyrido[3′,2′:4,5] thieno[3,2-d]pyrimidine derivatives

Pyrido [3′,2′:4,5]thieno[3,2-d] pyrimidine and several of its derivatives have been synthesized.     

Electrochemical properties of pyrido[1′,2′:1,2]imidazo[4,5-b]pyrazine and pyrido[1′,2′:1,2]imidazo[4,5-b]quinoxaline derivatives

The peak potentials (Ep) of 3-substituted pyrido[1′,2′:1,2]imidazo[4,5-b]pyrazine and pyrido[1′,2′:1,2]-imidazo[4,5-b]quinoxaline derivatives are sufficiently correlated with Hammett substituent constant ～_m and with the PM3 calculated LUMO energy levels, and the linear relationship between electron potentials of 9-substituted pyridoimidazoquinoxalines and the LUMO energy levels is also found out.     

Synthesis of novel pyrido[3′,2′:4,5]thieno[3,2‐d]pyrimidines,pyrido[3″,2″:4′,5′]thieno[3′,2′:4,5]pyrimido[l,6‐a]benzimidazoles and related fused systems

3‐Amino‐4‐aryl‐5‐ethoxycarbonyl‐6‐methylthieno[2,3‐b]pyridine‐2‐carboxamides 3a‐c were prepared from ethyl 4‐aryl‐3‐cyano‐6‐methyl‐2‐thioxo‐1,2‐dihydropyridine‐5‐carbonylates 1a‐c and reacted with some carbonyl compounds to give tetrahydropyridothienopyrimidine derivatives 6a‐c, 7a‐c and 8a‐c , respectively. Treatment of compound 3c with chloroacetyl chloride led to the formation of a next key compound, ethyl 2‐chloromethyl‐4‐oxo‐3,4‐dihydropyrido[3′,2′:4,5]thieno[3,2‐d]pyrimidine‐8‐carboxylate 9 . Also, 3‐amino‐2‐benzimidazolylthieno[2,3‐b]pyridine‐5‐carboxylate 5 and 2‐(3′‐aminothieno [2,3‐b]pyridin‐2′‐yl)‐4‐oxo‐3,4‐dihydropyrido[3′,2′:4,5]thieno[3,2‐d]pyrimidine‐8‐carboxylate 17 were prepared from 1c. The compounds 5, 9 and 17 were used as good synthons for other pyridothienopyrimidines and pyridothienopyrimidobenzimidazoles as well as for related fused polyheterocyclic systems.     

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.     

Fusions of pyrido[4′,3′:4,5]thieno[2,3-d]pyrimidines with N-heterocyclic moieties

Versatile 2-thioxopyrimidine-type building blocks ethyl 3-(2-ethoxy-2-oxoethyl)- 4 -oxo-2-thioxo-1,2,3,4,5,6,7,8-octahydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidine-7-carboxylate ( 4 ) and ethyl 4-oxo-2-thioxo-1,2,3,4,5,6,7,8-octahydropyrido[4′,3′:4,5]thieno[2,3-d]pyrimidine-7-carboxylate ( 8 ) were synthesized from diethyl 2-amino-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3,6-dicarboxylate ( 1 ). Derivatives of linear and angular heterocyclic systems having the imidazole and 1,2,4-triazole ring were obtained from the key intermediates 4 and 8 , respectively.     

The synthesis of novel polycyclic heterocyclic ring systems via photocyclization. 19. Thieno[3′,2′:4,5]thieno[2,3-c]-naphtho[1,2-f]quinoline,thieno[3′,2′:4,5]thieno[2,3-c]naphtho-[1,2-f][1,2,4]triazolo[4,3-a]quinoline and thieno[3′,2′:4,5]-thieno[2,3-c]naphtho[1,2-f]tetrazolo[1,5-a]quinoline

Photocyclization of 3-chloro-N-(3-phenanthryl)thieno[2,3-b]thiophene-2-carboxamide ( 5 ) yielded only one of the two possible structural isomers, thieno[3′,2′:4,5]thieno[2,3-c]naphtho[1,2-f]quinolin-6(5H)-one ( 6 ), which was further elaborated to afford the unsubstituted ring system 10 , its triazole 11 and tetrazole 12 . The structural confirmation of 10 was achieved by the total assignment of its ¹H and ¹³C nmr spectra by the concerted utilization of two-dimensional nmr spectroscopic methods.     

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).     

Synthesis of pyrido[1′,2′:1,2]imidazo[4,5-b]quinoxalines

Synthesis of pyrido[1′,2′:1,2]imidazo[4,5-b]quinoxalines by the facile cyclizations of 2,3-dichloroquinoxalines with 2-aminopyridines and of 2-amino-3-chloroquinoxalines with various substituted pyridines is described.     

Synthesis of two novel ring systems via photocyclization: Thieno[2′,3′:4,5]thieno[2,3-c][1,10]phenanthroline and thieno[3′,2′:4,5]thieno[2,3-c][1,10]phenanthroline

The synthesis of thieno[2′,3′:4,5]thieno[2,3-c][1,10]phenanthroline ( 5 ) and thieno[3′,2′:4,5]thieno-[2,3-c][1,10]phenanthroline ( 10 ) are described. Each compound was obtained in four steps from known starting materials. The basic skeleton of the molecule and of the phenanthroline ring were formed via photocyclization. The total assignment of ¹H-nmr spectra was accomplished with the aid of two-dimensional nmr methods.     

The synthesis of novel polycyclic heterocyclic ring systems via photocyclization. 17. Thieno[3′,2′:4,5]thieno[2,3-c]naphtho-[2,1-f]quinoline and thieno[3′,2′:4,5]thieno[2,3-c]-naphtho[1,2-g]quinoline

The synthesis of two previously unknown novel polycyclic heterocyclic ring systems via photocyclization is described. The structural assignment of the isomeric ring systems, 4 and 5 , was achieved by the total assignment of their ¹H and ¹³C nmr spectra by the concerted usage of two-dimensional nmr methods.     

Syntheses of 2,3‐dicyano‐5a,8a‐dihydro‐5a‐hydroxycyclopentano[1′,2′:4,5]pyrrolo[2,3‐b]pyrazines and 2,3‐dicyanocyclohexano[1′,2′:4,5]pyrrolo‐[2,3‐b]pyrazines

Previously synthesized 2‐(3′‐chloro‐5′,6′‐dicyanopyrazin‐2′‐yl)cyclopentan‐1‐one 1 , obtained from the reaction of 2,3‐dichloro‐5,6‐dicyanopyrazine with 1‐pyrrolidino‐1‐cyclopentene, was further reacted with primary alkylamines to give mixtures of diastereomer of 5‐alkyl‐2,3‐dicyano‐5a,8a‐dihy‐dro‐5a‐hydroxycyclopentano[1′,2′:4,5]pyrrolo[2,3‐b]pyrazines 3a‐h in high yield. The reaction of 2‐alkylamino‐3‐chloro‐5,6‐dicyanopyrazine with 1‐pyrrolidino‐1‐cyclohexene gave 5‐alkyl‐2,3‐dicyanocyclopentano[1′,2′:4,5]pyrrolo[2,3‐b]pyrazines 5a‐b together with 5‐alkylamino‐2,3‐dicyano‐6‐pyrrolidinopyrazines 6a‐b . The products prepared are all of interest as potential pesticides and new fluorescent chromophores.     

The synthesis of novel polycyclic heterocyclic ring systems via photocyclization. 1. Thieno[3′,2′:4,5]thieno[2,3-c]quinoline and thieno[2′,3′:4,5]thieno[2,3-c]quinoline

The synthesis of two previously unknown heterocyclic ring systems, namely, thieno[3′,2′:4,5]thieno[2,3-c]-quinoline and thieno[2′,3′:4,5]thieno[2,3-c]quinoline is reported. These two novel ring systems were assembled by photocyclization of the appropriate anilides.     

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 .     

Synthesis of pyrido[1′,2′:1,2]imidazo[4,5-b]pyrazines from 2-amino-3-chloro-5,6-dicyanopyrazine with substituted pyridines

Novel synthesis of the title compounds by the cyclization between 2-amino-3-chloro-5,6-dicyanopyrazine and various substituted pyridines is described.     

The synthesis of novel polycyclic heterocyclic ring systems via photocyclization. 16. [1]benzothieno[2′,3′:4,5]thieno[2,3-c]quinoline and [1]benzothieno[2′,3′:4,5]thieno[2,3-c]naphtho[1,2-f]quinoline

The synthesis of two previously unknown polycyclic heterocyclic ring systems via photocyclization is described. The unequivocal assignment of their proton and carbon spectra was achieved by utilizing two-dimensional nmr techniques.     

Studies of thieno[2,3-b]pyrazines in preparation of pyrazino[2′,3′:4,5]thieno[3,2-d]pyrimidines and related molecules

A variety of 2,3-disubstituted derivatives of the previously unknown thieno[2,3-b]pyrazine ring system have been employed as a synthetic foundation for pyrazino[2′,3′:4,5]thieno[3,2-d]-pyrimidine and several of its derivatives.     

An efficient synthesis of new pyrido[4′,3′:4,5]thieno[2,3‐d]‐pyrimidin‐4(3H)‐one derivatives

The carbodiimides 5 , obtained from reactions of iminophosphorane 4 with aromatic isocyanates, reacted with amines, phenols or ROH to give 2‐substituted 5,6,7,8‐tetrahydropyrido[4′,3′:4,5]thieno[2,3‐d]‐pyrimidin‐4(3H)‐one 7 in the presence of catalytic amount of sodium alkoxide or solid potassium carbonate in satisfactory yields.     

Synthesis of β‐Lactam‐containing Pyrido[3′,2′:4,5]thieno[3,2‐e][1,4]diazepines

Novel tricyclic 1,4‐diazepine derivatives – pyrido[3′,2′:4,5]thieno[3,2‐e ][1,4]diazepin‐2‐ones – have been synthesized. Azetidin‐2‐one moiety has been incorporated into the 1,4‐diazepine scaffold by [2 + 2]cycloaddition of functionalized ketenes to imine C═N bond, and several tetracyclic azetodiazepines which can be considered as potential compounds of biological interest have been prepared. Stereoselectivity of the cycloaddition was proved by NMR and X‐ray analysis data.