Synthesis of imidazo[4,5-d]pyridazine nucleosides related to inosine

Several imidazo[4,5-d]pyridazine nucleosides which are structurally similar to inosine were synthesized. Anhydrous stannic chloride-catalyzed condensation of persilylated imidazo[4,5-d]-pyridazin-4(5H)one (1) and imidazo[4,5-d]pyridazine-4,7(5H,6H)dione ( 16 ) with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose ( 3 ) provided (after sodium methoxide deblocking) 6-β-D-ribo furanosylimidazo[4,5-d]pyridazin-4(5H)one (5) and 3,6-di-(β-D-ribofuranosyI)imidazo[4,5-d]pyridazin-4-one ( 7 ); and 1-(β-D-ribofuranosyl)imidazo[4,5-d]pyridazine-4,7(5H,6H)dione ( 19 ) and 1,5 or 6-di-(β-D-ribofuranosyl)imidazo[4,5-d ]pyridazine-4,7(5H or 6H)dione ( 21 ), respeeitvely. 4,7-Diehloro-1-β-D-ribofuranosylimidazo[4,5-d]pyridazine ( 12 ) and dimethyl 1-β-D-ribofuranosylimidazole-4,5-dicarboxylate ( 26 ), both prepared from stannic chloride-catalyzed ribosylations of the corresponding heterocycles, were converted in several steps to 3-β-D-ribo-furanosy limidazo[4,5-d]pyridazin-4(5H)one ( 14 ) and nucleosidc 19 , respectively. Acid-catalyzed isopropylidenation of mesomeric betaine 7 or nuclcoside 14 provided 3-(2,3-isopropylidene-β-D-ribofuranosyl)imidazo[4,5-d]pyrizin-4(5H)one ( 31 ). 1-β-D-Ribofuranosylimidazo[4,5-d]-pyridazine ( 29 ) was obtained in several steps from nueleoside 12 . The structure of the nucleosides was established by the use of carbon-13 and proton nmr.     

The synthesis of novel polycyclic heterocyclic ring systems via photocyclization. 6. Naphthothienonaphthyridines

Five novel polycyclic heterocyclic ring systems are reported via photocyclization. The specific final products in these ring systems are: naphtho[1′,2′:4,5]thieno[2,3-c][1,8]naphthyridin-6(5H)-one ( 5 ), naphtho-[1′,2′:4,5]thieno[2,3-c][1,6]naphthyridin-6(5H)-one ( 6 ), naphtho[1′,2′:4,5]thieno[2,3-c]-1,5-naphthyridine ( 9 ), naphtho[1′,2′:4,5]thieno[2,3-c][1,2,4]triazolo[4,3-a]-1,5-naphthyridine ( 12 ), and naphtho[2′,1′:4,5]thieno[2,3-c]-1,5-naphthyridine ( 17 ). The direction of photocyclization to produce 9 was established from a zero quantum two-dimensional nmr spectroscopy experiment (ZQCOSY) using 6-chloronaphtho[1′,2′:4,5]thieno[2,3-c]-1,5-naphthyridine ( 8 ) as the model compound.     

Pyrolysis and photolysis of 1-aroylamino-4,5-diaryl-1,2,3-triazoles: Generation and thermal transformations of 4,5-diaryl-1,2,3-triazolyl radicals

The pyrolysis of 1-aroylamino-4,5-diphenyl-1,2,3-triazoles 1 yields, pressumably via the 4,5-diphenyl-1,2,3-triazolyl radical ( 2a ), 2,3-diphenyl-2H-azirine ( 11a ) and 2-aryl-4,5-diphenylimidazoles 14 as the major products. Upon irradiation 1-benzoylamino-4,5-diphenyl-1,2,3-triazole ( 1a ) gives 4,5-diphenyl-1 (2)H-1,2,3-triazole ( 4a ) via the 1,2,3-triazolyl radical 2a , together with benzamide ( 5a ) and 1,2-bisbenzoylhydrazine ( 6a ). Products 5a and 6a result from the benzoylamino radical 3a by hydrogen atom abstraction and dimerization respectively.     

Synthesis of some new derivatives of 4-hydrazino-5H-pyridazino[4,5-b]indole

This paper describes the synthesis of 1-chloro-4-hydrazino-5H-pyridazino[4,5-b]indole ( 4 ) and some of the triazoles ( 6–8 ), tetrazoles ( 10–11 ), triazolotetrazoles ( 9 ) and bis-tetrazoles ( 12 ) derived from it. All of these were previously unknown compounds. Treating 1,4-dioxo-1,2,3,4-tetrahydro-5H-pyridazino[4,5-b]indole ( 1 ) with phosphorus oxychloride gave 1,4-dichloro-5H-pyridazino[4,5-b]indole ( 2 ), which reacts regioselectively with hydrazine to give compound 4 . The reactions of 4 with formic and acetic acids gave 6-chloro-11 H-1,2,4-triazolo[4,3-b]pyridazino[4,5-b]indoles ( 6a-6b ), respectively. Reaction of compound 6a with hydrazine gave 6-hydrazino-11H-1,2,4-triazolo[4,3–6]-pyridazino[4,5,-b]indole ( 8 ). This with nitrous acid gave 6-azido-11H-1,2,4-triazolo[4,3-b]pyridazino[4,5-b]-indole ( 9 ). Compound 4 reacted with nitrous acid to give 6-chloro-11H-tetrazolo[4,5-b]pyridazino[4,5-b]-indole ( 10 ), which gave 1,4-diazydo-5H-pyridazino[4,5-b]indole ( 12 ), through successive reactions with hydrazine and nitrous acid. All compounds were characterized by elemental analysis, ir and ¹H-nmr spectra.     

The synthesis of imidazo[4,5-c] - and v-triazolo[4,5-c] pyridazines

The parent imidazo[4,5-c]pyridazine (IV) has been prepared for the first time by three different routes. 1-Methylimidazo[4,5-c]pyridazine (XX) and 3-methylimidazo[4,5-c]pyridazine (XXVII) have been prepared by unequivocal syntheses. The constitution of the methylation product of imidazo[4,5-c]pyridazine-2-thiol (VIII) has been shown to be 2-methylthioimidazo[4,5-c]-pyridazine (IX) by the unequivocal syntheses of 1-methylimidazo[4,5-c]pyridazine-2-thiol (XXIII) and 3-methylimidazo[4,5-c]pyridazine-2-thiol (XXXIII). Likewise, the structure of the methylation product (XIII) was shown to be S-methylation by the unequivocal syntheses of 1-methyl-2-methylthio-6-chloroimidazo[4,5-c]pyridazine (XXIV) and 3-methyl-2-methylthio-6-chloroimidazo[4,5-c]pyridazine (XXXI), respectively. Several 7-substituted amino-v-triazolo-[4,5-c]pyridazines (XXXVIII) have been prepared from 7-chloro-v-triazolo[4,5-c]pyridazine (XXXVII).     

The crystal and molecular structure of 5-N-methyl-β-d-arabinofurano[1′,2′:4,5]oxazolo-S-triazine-4,6-dione: Molecular modeling studies on the pattern of alkylation of β-D-arabinofurano[1′,2′:4,5]oxazolo-s-triazin-4-one-6-thione

The involvement of the 5′-hydroxyl group on β-D-arabinofurano[1′,2′:4,5]oxazolo-s-triazin-4-one-6-thione ( 1b ), to form an intramolecular covalent adduct at C6, is postulated to explain the formation of almost equal amounts of 5-N-alkyl-β-D-arabinofurano[1′,2′:4,5]oxazolo-s-triazin-4-one-6-thione and 5-N-alkyl-β-D-arabinofurano[1′,2′:4,5]oxazolo-s-triazine-4,6-dione during alkylation of 1b . An X-ray crystallographic study was conducted on 5-N-methyl-β-D-arabinofurano[1′,2′:4,5]oxazolo-s-triazine-4,6-dione ( 2a ) and its solid state structure was established. This was compared to the energy minimized structure of the same compound that was generated by the molecular modeling program, MACROMODEL. Force field calculations (Allinger's MM2) on this structure and other intermediates lend support to the concept of formation of the intramolecular covalent adduct.     

The reaction of aromatic α,β-unsaturated ketones with 4,5-diamino-1,6-dihydropyrimidin-6-ones

The reaction of 4,5-diamino-1,6-dihydropyrimidin-6-ones 1 with one equivalent of the chalcones 2 leads in an acidic medium to the formation of the 2,4-diaryl-2,3,6,7-tetrahydro-1H-pyrimido[4,5-b][1,4]diazepin-6-ones 3a-m . The structure elucidation of the products is based on detailed nmr investigations including selective ¹³C[¹H] decoupling experiments.     

Synthesis of 8-methyl-2-azainosine and related nucleosides

The synthesis of 6-methyl-7-(β-D-ribofuranosyl)imidazo[4,5-d]-v-triazin-4-one (8-methyl-2-azainosine ( 2) ) and 6-methyl-7-(β-D-glucopyranosyl)imidazo[4,5-d]-v-triazin-4-one ( 5 ) by diazotization of 5-amino-1-(β-D-ribofuranosyl)-2-methylimidazole-4-carboxamide ( 1 ) and diazotization of 5-amino-1-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-2-methylimidazole-4-carboxamide ( 3 ), followed by deacetylation of the resulting compound 4 , is described. The preparation of 6-methyl-5-(β-D-ribofuranosyl)imidazo[4,5-d]-v-triazin-4-one ( 10 ) and 6-methyl-5-(β-D-glucopyranosyl)imidazo[4,5-d]-v-triazin-4-one ( 11 ) by glycosylation of 6-methylimidazo[4,5-d]-v-triazin-4-one (8-methyl-2-azahypoxanthine, ( 7) ) is also described. Structural assignments were made on basis of analytical and ¹H-nmr and uv spectral data.     

Palladium(0)-catalyzed phenylation of imidazo[4,5-b]pyridines

The tetrakis(triphenylphosphine)palladium(O)-catalyzed coupling of benzeneboronic acid with 2-chloro, 6-bromo and 6-bromo-2-chloro derivatives of 1- and 3-methylimidazo[4,5-b]pyridines to novel 2-phenyl-, 6-phenyl- and 2,6-diphenylimidazo[4,5-b]pyridines is described. The phenylation of imidazo[4,5-b]-pyridines containing labile hydrogens was not successful.     

Thiazolo[4,5-d]pyrimidines. Part I. synthesis and anti-human cytomegalovirus (HCMV) activity in vitro of certain alkyl derivatives

Alkyl derivatives of the thiazolo[4,5-d]pyrimidine congeners of guanine and uracil were prepared and assessed for in vitro activity against human cytomegalovirus (HCMV). The finding that the 3-pentyl 1b and 3-hexyl 1c derivatives of 5-aminothiazolo[4,5-d]pyrimidine-2,7(3H,6H)-dione (1e) had potent in vitro anti-HCMV activity prompted a broader study of alkyl derivatives in this ring system. A series of 3-alkyl derivatives of 1e , viz. 1f-w , were prepared by direct alkylation of the sodium salt of 1e and by subsequent modifications, 2a-d. For comparison with 1c , 5-amino-2-hexylaminothiazolo[4,5-d]pyrimidin-7(6H)-one (4) was prepared and studied. The 3-(2-alkenyl) derivatives of 1e were found to be the more active antiviral agents with the Z isomer of 5-amino-3-(2-penten-1-yl)thiazolo[4,5-d]pyrimidine-2,7(3H,6H)-dione (1f) having the better therapeutic index. Analogous 4-(2-alkenyl) derivatives of 2-aminothiazolo[4,5-d]pyrimidine-5,7(4H,6H)-dione 6a and 6b were also prepared but were found to have poor therapeutic indices. Single crystal X-ray diffraction analysis was used to unequivocally establish the structure of 1f.     

Reaction of 6-arylidenehydrazino-1,3-dimethyluracils with thionyl chloride leading to purine,thiazolo[4,5-d]pyrimidine,pyrimido[4,5-e][1,3,4]thiadiazine,pyrazolo[3,4-d]pyrimidine,and [1,2,3]thiadiazolo[4,5-d]pyrimidine derivativese

The reaction of 6-arylidenehydrazino-1,3-dimethyluracils with thionyl chloride in benzene afforded purine, thiazolo[4,5-d]pyrimidine, pyrimido[4,5-e][1,3,4]thiadiazine, pyrazolo[3,4-d]pyrimidine, and [1,2,3]thiadiazolo[4,5-d]pyrimidine derivatives, while the treatment of 6-(benzylidene-1′-methylhydrazino)-1,3-dimethyluracil with thionyl chloride in benzene gave 4-methylpyrimido[4,5-e][1,3,4]thiadiazine and 1-methylpyrazolo-[3,4-d]pyrimidine derivatives. Plausible mechanisms for the formation of these fused pyrimidines are also described.     

Halogenation of Imidazo[4,5-<Emphasis Type="Italic">b</Emphasis>]pyridin-2-one Derivatives

Chlorination and bromination of 2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-one and its N-methyl-substituted derivatives in acetic acid at 90–95°C leads to formation of the corresponding 5,6-dichloro(dibromo)-2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-ones. Iodination of the same substrates with ICl under analogous conditions yields 6-iodo derivatives. Chlorination of 6-iodo-1,3-dimethyl-2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-one is accompanied by replacement of the iodine atom by chlorine with formation of 5,6-dichloro-1,3-dimethyl-2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-one. Bromination of 6-bromo- and 6-chloro-2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-ones gives 5,6-dibromo- and 5-bromo-6-chloro-2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-ones, respectively.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 4, 2005, pp. 586–589.Original Russian Text Copyright © 2005 by Yutilov, Lopatinskaya, Smolyar, Gres’ko.     

Synthesis of a new isomer of creatinine and its use in the preparation of the food mutagen 2-amino-1-methyl-6-phenyl-1H-imidazo[4,5-b]pyridine (PHIP)

Base-induced cyclization of N′-cyanomethyl-N′-methylurea gives 1-methyl-4-amino-imidazol-2-one, this in turn is condensed with 3-hydroxy-2-phenylacrolein to yield an imidazo[4,5-b]pyridine which is converted into 2-amino-1-methyl-6-phenyl-1H-imidazo[4,5-b]pyridine (PHIP).     

Nucleophilic Substitution in the Allylic System of Codeine and Pseudocodeine: Reactions with lithium cyano(methyl)-and (aryl)cyanocuprates. Crystal and molecular structure of 8α-phenyl-6,7-didehydro-4,5α-epoxy-3-methoxy-17-methylmorphinan and 6α-phenyl-7,8-didehydro-4,5α-epoxy-3-methoxy-17-methylmorphinan

Nucleophilic substitution of 6β-chloro-7,8-didehydro-4,5α-epoxy-3-methoxy-17-methylmorphinan ( 1 ) and 8α-bromo-6,7-didehydro-4,5α-epoxy-3-methoxy-17-methylmorphinan ( 2 ) with lithium cyano(methyl)- and (aryl)cyanocuprates(I) ( 5a–c ) was accompanied by allylic rearrangement with both change and retention of orientation of the substituting group (Scheme 1, Table 1). Nucleophilic substitution in 7,8-didehydro-4,5α-epoxy-3-methoxy-17-methylmorphinan-6α-yl methanesulfonate ( 3 ) and 7,8-didehydro-4,5α-epoxy-3-methoxy-17-methylmorphinan-6β-yl methanesulfonate ( 4 ) proceeded without allylic rearrangement with both change and retention of the orientation of the substituting group (Scheme 2, Table 1). X-Ray diffraction studies of the products 6,7-didehydro-4,5α-epoxy-3-methoxy-17-methyl-8α-phenylmorphinan ( 6b ) and 7,8-didehydro-4,5α-epoxy-3-methoxy-17-methyl-6β-phenylmorphinan ( 7b ) were carried out (Figs. 1 and 2).     

α-Thioureidoalkylation of functionally substituted ureas: I. Tandem cyclization and esterification in reactions of <Emphasis Type="Italic">N</Emphasis>-(carboxyalkyl)ureas with 1,3-dialkyl-4,5-dihydroxy-4,5-diphenylimidazolidine-2-thiones in alcohols

Acid-catalyzed reactions of N-(carboxyalkyl)ureas with 1,3-dialkyl-4,5-dihydroxy-4,5-diphenylimidazolidine-2-thiones in methanol or propan-2-ol led to the formation of previously unknown ω-(4,6-dialkyl-2-oxo-3a,6a-diphenyl-5-thioxooctahydroimidazo[4,5-d]imidazol-1-yl)alkanoic acids and their methyl and isopropyl esters. The structure of some esters was proved by X-ray analysis. Methyl (4,6-diethyl-2-oxo-3a,6adiphenyl-5-thioxooctahydroimidazo[4,5-d]imidazol-1-yl)acetate showed anxiolytic effect.     

Retro-ene reaction. II. Reaction of 4,5-dichloro-1-hydroxy-methylpyridazin-6-one with alkyl halides and carboxylic acid chlorides

1-Alkyl-4,5-dichloropyridazin-6-oncs and (4,5-dichloro-6-oxopyridazin-1-yl)methylcarboxylates were synthesized from 4,5-dichloro-1-hydroxymethylpyridazin-6-one and the corresponding alkyl halides or carboxylic acid chlorides. Also the reaction mechanisms via a fragmentation of retro-ene type are discussed.     

Purines, pyrimidines, and related fused systems. 21. Oxidative amination of 3-chloro-6,8-dimethylpyrimido[4,5-c]pyridazine-5,7(6H,8H)-dione

Oxidative amination of 3-chloro-6,8-dimethylpyrimido[4,5-c]pyridazine-5,7(6H,8H)-dione with primary alkylamines and potassium amide in liquid ammonia gives rise to the corresponding 4-amino derivatives as the major products. The reactions with acyclic secondary amines are accompanied by annelation of the pyrrole moiety to the starting heterosystem to form 1-R-3-R"-6,8-dimethylpyrrolo[2",3";3,4]pyrimido[4,5-c]pyridazine-7,9(6H,8H)-diones. The reaction with piperidine as the aminating agent occurs exclusively as aminodehalogenation. The Sonogashira cross-coupling of 4-amino-3-chloro-6,8-dimethylpyrimido[4,5-c]pyridazine-5,7(6H,8H)-diones with terminal alkynes affords 1-R-2-R"-6,8-dimethylpyrrolo[3",2";3,4]pyrimido[4,5-c]pyridazine-7,9(6H,8H)-diones.     

Retro-ene reactions. III. Alkylation of 4,5-dichloro-1-hydroxymethylpyridazin-6-ones: Synthesis of 4,5-dichloro-1-(ω-phthalimido and saccharin-2′-ylalkyl)pyridazin-6-ones

4,5-Dichloro-1-(ω-phthalimido and saccharinyl-2′-ylalkyl)pyridazin-6-ones were synthesized from 4,5-dichloro-1-hydroxymethylpyridazin-6-one and the corresponding N-(ω-haloalkyl)phthalimides and saccharins via a fragmentation of retro-ene type.     

The synthesis of proximal-benzolumazine,proxirnal-benzoxanthine,proximal-benzotheophylline and proximal-benzocaffeine

The synthesis of pyrazino[2,3-f]quinazolin-8,10-(7H,9H)dione(proximal-benzolumazine, 1 ), imidazo[4,5-f]-quinazolin-7,9-(6H,8H)-dione (proximal-benzoxanthine, 2 ), 6,8-dimethylimidazo[4,5-f]-quinazolin-7,9-(6H,8H) dione (proximal-benzotheophylline, 3 ), and 1,6,8-trimethylimidazo[4,5-f]quinazolin-7,9-(6H,8H)dione (proximal-benzocaffeine, 4 ) is reported by commencing with 2-amino-6-chlorobenzamide and proceeding via a variety of 5,6-disubstituted-2,4-(1H,3H)quinazolinediones. Methylation of 3 is shown to yield 3,6,8-trimethylimidazo[4,5-f]quinazolin-7,9-(6H,8H)dione ( 15 ) and 4 in a ratio of 4:1.     

Crystal Structure and Magnetic Properties of Pyridyl-Substituted Nitronyl Nitroxides

X-ray crystal structure and cryomagnetic properties of three organic radicals, 2-(2-pyridyl)-4, 4,5,5-tetramethyl-4,5-dihydro-1-H-imidazol-1-oxyl-3-N-oxide(NIT-oPy) 1, 2-(3-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-l-H-imidazol-1-oxyl-3-N-oxide(NIT-mPy) 2 and 2-(6-methyl-2-pyridyl)-4,4,5,5-tetramethyl-4, 5-dihydro-1-H-imidazol-1-oxyl-3-N-oxide(NIT-6M-oPy) 3 were investigated. The crystal structures of compounds 1-3 show the same feature of a P2₁/c space group of a monoclinic system. Two crystallographically independent molecules were found in the crystals of compounds 1-3. The temperature dependence of magnetic susceptibility of compounds 1-3 revealed an intermolecular antiferromagnetic exchange interaction.