Pyridinethiones—II : Preparation of condensed pyridines related to 3-formyl-2(1H,-pyridinethione

Some condensed pyridines, isothiazolo[4,5-b]pyridine, 2-oxo-2$\text{H}$-thiopyranyl[5,6-b]pyridines, and thieno[3,2-b]pyridines, have been prepared from 3-formyl-2(1$\text{H}$)-pyridinethione or the 1-substituted precursors for this compound.     

Photocyclization of benzofurancarboxanilides. Photorearrangement of the benzodihydrofuran system to 3-o-hydroxyphenylquinolones

$\text{cis}$-Dihydrobenzofuro[2,3-c]quinolone ($\text{4a}$) and $\text{cis}$-dihydrobenzofuro-[3,2-c]quinolone ($\text{5}$) undergo photorearrangement, characteristic to the benzodihydrofuran system, leading to 3-$\text{o}$-hydroxyphenylquinolone ($\text{6}$). A plausible mechanism involving a cyclopropyl dienone ($\text{12}$) was discussed.     

SYNTHESIS OF PYRIDAZOTHIENOTHIAZINE AND PYRIMIDOTHIENOPYRIDAZINES

Abstract

3-amino-4,5-diphenylthieno[2,3-c]pyridazine-2-arylcarboxamide 2 underwent cyclization with triethyl orthoformate and with nitrous acid to give the pyrimidothienopyridazines 3a-c, 4b respectively. 3-amino-4,5-diphenylthieno[2,3-c] pyridazine-2-carbohydrazide 6 reacted with aromatic aldehydes to give the corresponding carbohydrazones 7a-c. Compound 7 reacts with triethyl orthoformate, acetic anhydride or with CS₂/pyridine to produce pyrimidothienopyridazines 8,9 and pyridazothienothiazine 11.     

Palladium-catalyzed cyclization reactions of 3-propargylthio 1,2,4-triazin-5(2h)-ones to thiazolo-1,2,4-triazinones

Selective transformation of 3-propargylthio-1,2,4-triazin-5(2H)-ones ($\text{1}$) to 6-methylene-6,7-dihydro-4H-thiazolo[2,3-c][1,2,4]-triazin-4-ones ($\text{2}$) and 3-methylene-2,3-dihydro-7H-thiazolo[3,2-b]-[1,2,4]triazin-7-ones ($\text{3}$) is performed under the conditions of Pd(II) salt or sodium hydroxide catalysis, respectively.     

Cycloaddition of diphenylnitrilimine to coumarins. The synthesis of 3a,9b-dihydro-4-oxo-1H-benzopyrano [4 ,3-c]pyrazole derivatives

The cycloaddition of diphenylnitrilimine to a series of coumarins occurs with the same regioselectivity in all cases, regardless the nature of the substituent present, to yield the corresponding 3a,9b-dihydro-4-oxo-lH-benzopyrano [4,3-c]pyrazoles $\text{4}$a–f. Dehydrogenation of $\text{4a}$ yields 4-oxo-1H-benzopyrano [4,3-c]-pyrazole $\text{6}$. In ethanolic sodium ethoxide solution, the reaction between coumarin and diphenylnitrilimine precursor, namely N-phenylbenzohydrazidoyl chloride $\text{1}$, affords no cycloadducts, but yields o-(β-ethoxycarbonylvinyl)phenyl N-phenylbenzohydrazidate $\text{10}$. The regiochemistry of the cycloadducts $\text{4}$a–f and the reaction sequence leading to $\text{10}$ are outlined. The structures of the products have been established by spectroscopic methods and independent syntheses wherever possible.     

Palladium-catalyzed cyclization reactions : Unique synthesis of condensed thiazoles

The facile synthesis of 3-methylene-2,3-dihydro-5H-thiazolo-[3,2-c]pyrimidin-5-ones ($\text{9}$) has been performed by the catalytic action of a Pd(II) salt on 4-propargylthiopyrimidin-2(1H)-ones ($\text{6}$).Similar Pd(II)-catalyzed cyclization of 3-propargylthio-1,2,4-triazin-5(2H)-ones ($\text{10}$) gives 6-methylene-6,7-dihydro-4H-thiazolo[2,3-c](1,2,4]-triazin-4-ones ($\text{11}$) as a main product. 3-Methylene-2,3-dihydro-7H-thiazolo[3,2-b][1,2,4]triazin-7-ones ($\text{12}$), the regioisomers of $\text{11}$ are provided by a base-catalyzed cyclization of [ulbar 10].     

Reaction of 2-functionalized pyrylium salts with amidrazones

A number of derivatives of the bicyclic 1,2,4-triazolo [1,5-a] pyridine ($\text{3}$) and pyrido [2,1-f][1,2,4] triazine ($\text{4}$ and $\text{7}$) have been prepared by reaction of 2-methylthio- and 2-ethoricarbonyl-4, 6-diphenylpyrylium salts, respectively, with amidrazones.     

咪唑并吡啶类化合物的合成及其应用*

咪唑并吡啶类化合物具有与吲哚、氮杂吲哚等类似的特殊结构和良好的生物活性,在医药和农药工业有着广泛的应用,成为有机化学家和药物化学家的研究热点。咪唑并吡啶类化合物主要有咪唑并[4,5-b]吡啶、咪唑并[4,5-c]吡啶、咪唑并[1,2-a]吡啶和咪唑并[1,5-a]吡啶等4个类型。本文阐述了近年来咪唑并吡啶类化合物的合成研究进展和应用情况,主要介绍了咪唑并[4,5-b]吡啶和咪唑并[4,5-c]吡啶这两类化合物的合成方法和在医药及农药领域的应用。     

Bridgehead nitrogen heterocycles from 2,4,6-triphenyl- pyrylium cation and thiosemicarbazide or thiocarbohydrazide

2,4,6-Triphenylpyrylium with thiosemicarbazide and thiocarbohydrazide, gives 2-pyrazolines $\text{3a}$ and $\text{3b}$ which undergo cyclization yielding pyrazolo(1,5-c]pyrimidine 5 and pyrazolo [2,3-d]-1,2,4-triazepine $\text{7}$ derivatives, respectively. Reaction of $\text{7}$ with phenacyl bromides gave 1,3-thiazolo[3,2-b]pyrazolo [2,3-d]-1,2,4-triazepin-4-iums $\text{10}$. Compound $\text{3a}$ on treatment with phenacyl bromides gave 1-(4'-aryl-thiazol-2'-yl)-2-pyrazoline derivatives $\text{6}$. Compound $\text{3b}$ reacts with acyl chlorides to give pyrazolo[1,5-c]pyrimidine derivatives $\text{14}$, and with aromatic aldehydes giving the 2-(Δ^2'1 pyrazolin-1-yl)-5-aryl-1,3,4-Δ²-thiadiazolines $\text{12}$ which were easily converted to the corresponding 2-(Δ²-pyrazolin-1-yl)-5-aryl-1,3,4-thiadiazoles $\text{13}$.     

Synthesis of 3-Deaza-2′-deoxyadenosine and 3-Deaza-2′,3′-dideoxyadenosine: Glycosylation of the 4-Chloroimidazo[4,5-c]pyridinyl Anion

The convergent syntheses of 3-deazapurine 2′-deoxy-β-D -ribonucleosides and 2′,3′-dideoxy-D -ribonucleosides, including 3-deaza-2′-deoxyadenosine ( 1a ) and 3-deaza-2′,3′-dideoxyadenosine ( 1b ) is described. The 4-chloro-lH-imidazo[4,5-c]pyridinyl anion derived from 5 was reacted with either 2′-deoxyhalogenose 6 or 2′,3′-dideoxyhalogenose 10 yielding two regioisomeric (N¹ and N³) glycosylation products. They were deprotected and converted into 4-substituted imidazo[4,5-c]pyridine 2′-deoxy-β-D -ribonucleosides and 2′,3′-dideoxy-D -ribonucleosides. Compounds 1a and 1b proved to be more stable against proton-catalyzed N-glycosylic bond hydrolysis than the parent purine nucleosides and were not deaminated by adenosine deaminase.     

Vibrational spectra and structure of methyl-derivatives of imidazo[4,5-c]pyridine based on DFT quantum chemical calculations and XRD studies

The molecular structures, vibrational energy levels and potential energy distribution of 4-methyl-imidazo[4,5-c]pyridine (4MIPc) and 7-methyl-imidazo[4,5-c]pyridine (7MIPc) are derived from the quantum chemical calculations and compared to the experimental results obtained from the X-ray diffraction (XRD), IR and Raman studies. The B3LYP/6-311G(2d,2p) quantum model and PED contributions have been applied for the assignment of the vibrational modes. 4MIPc crystallizes in an orthorhombic structure, space group Pna2₁ and Z = 4 and 7MIPc crystallizes in a triclinic structure, space group P−1 and Z = 4. The almost planar conformation of the molecules and presence of the N–H?N hydrogen bonds formed with the pyridine and imidazole nitrogen atoms was found to be characteristic for the studied systems. The presence of hydrogen bonds is also confirmed by the results of IR studies.     

A concise synthesis of all four possible benzo[4,5]furopyridines via palladium-mediated reactions

[reaction: see text] By taking advantage of the alpha- and gamma-activation of chloropyridines as well as palladium-mediated reactions, all four possible benzo[4,5]furopyridine tricyclic heterocycles, benzo[4,5]furo[2,3-b]pyridine, benzo[4,5]furo[2,3-c]pyridine, benzo[4,5]furo[3,2-c]pyridine, and benzo[4,5]furo[3,2-b]pyridine, are efficiently synthesized from 2-chloro-3-iodopyridine, 3-chloro-4-stannylpyridine, 4-chloro-3-iodopyridine, and 2-chloro-3-hydroxypyridine, respectively.     

Reactions of 5-[3-(trifluoromethyl)-phenyl]furan-2-carbaldehyde

The Knoevenagel condensations of 5-[3-(trifluoromethyl)phenyl]furan-2-carbaldehyde with seven compounds containing an active methyl or methylene group have been studied. The compounds used were: methyl 2-cyanoacetate, malononitrile, 2-furylacetonitrile, acetophenone, 2-thioxo-1,3-thiazolidin-4-one (rhodanine), 5,5-dimethylcyclohexane-1,3-dione (dimedone), and methyl 2-azidoacetate. The effect of microwave irradiation on the condensation reactions was studied and compared with “’classical”’ conditions. Thermolysis of methyl 2-azido-3-{5-[3-(trifluoromethyl)phenyl]-2-furyl}propenoate afforded methyl 2-[3-(trifluoromethyl)phenyl)]-4H-furo[3,2-b]pyrrole-5-carboxylate. (2E)-3-{ 5-[3-(Trifluoromethyl)phenyl]-2-furyl}propenoic acid was converted to the corresponding azide, which was cyclized on heating into 2-[3-(trifluoromethyl)phenyl)]-4,5-dihydrofuro[3,2-c]pyridin-4-one. The latter after successive action of POCl₃ and NH₂NH₂-Pd/C gave 2-[3-(trifluoromethyl)-phenyl]furo[3,2-c]pyridine. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 825–831, June, 2006.     

4-Acetoxytricyclo[4.1.0.02,7]Hept-4-en-3-one; synthesis and novel bond reorganization of a valence isomer of 2-acetoxytropone

4-Acetoxytricyclo[4.1.0.0^2,7]hept-4-en-3-one ($\text{3}$), a valence isomer of 2-acetoxytropone, was synthesized. Upon heating in pyridine at 150°C, $\text{3}$ rearranged into 1-acetoxybicyclo[3.2.0]hepta-3,6-dien-2-one ($\text{9}$); the mechanism of which was examined by means of deuterium labeling experiments.     

Intramolecular cyclizations of allyl- and propargylsilanes

Allylsilanes of type $\text{5}$ and propargylsilanes of type $\text{13}$ undergo efficient cyclizations upon treatment with EtAlCl₂ in toluene to afford stereoselectively functionalized hydrindanones of type $\text{6}$ and spiro[4,5]decanes of type $\text{14}$.     

A novel route to meta-aminobenzotrifluoride

Product patterns can be altered in reactions of $\text{m}$-nitrobenzotrichloride [VI] with [AHF]_x·NH₄F complex. Side-chain fluorination predominates under ‘mild’ conditions. In contrast. ‘forcing’ conditions affected unexpected $\text{in}$-$\text{situ}$ fluorination-reduction to give $\text{m}$-aminobenzotrifluoride [V] in high yield [75%] and purity [99.6%]. $\text{in}$-$\text{situ}$ reduction is probably initiated by a combination of iron from the stainless steel autoclave and trace amounts of moisture. The transformation of [VI] to [V] represents another type of $\text{in}$-$\text{situ}$ fluorination-reduction nitroaromatics, e.g. nitrobenzene [VII] to $\text{p}$-fluoroaniline [VIII]. $\text{o}$-Nitrobenzotrichloride [XI] degraded under ‘forcing’ conditions with [AHF]_x·NH₄F.     

Alkaline hydrolysis of 2-(trifluoromethyl)imidazo[4,5-f] and -[4,5-h]quinolines

2-(Trifluoromethyl)imidazo[4,5-$\text{f}$] and -[4,5-$\text{h}$]quinoline have been prepared from 5(6),acetamido-2-(trifluoromethyl)benzimidazole and 7,8-diaminoquinoline respectively. These (trifluoromethyl)- quinolines like 2-(trifluoromethyl)imidazoles but unlike 2-(trifluoromethyl) benzimidazoles, undergo hydrolysis in dilute sodium hydroxide to give ultimately the corresponding imidazo[4,5-$\text{f}$] and -[4,5-$\text{h}$]- quinoline, respectively.     

Ring transformation of 4-oxo-1,6,7,8-tetrahydro-4H-pyrido[1,2-a]-pyrimidine-3-carboxamide

The title compound /$\text{3}$/ may be transformed into the 3-/methylaminomethylene/--2,3,6,7,8,9-hexahydro-4H-pyrido[1,2-a]pyrimidine-2,4-dione /$\text{5}$E, $\text{5}$Z/ which is in equilibrium with the 1,2,3,6,7,8-hexahydro tautomer /$\text{8}$E, $\text{8}$Z/ in DMSO-d₆.     

Nature of the catalytic cycle in iridium-complex catalysed hydrogenation of unsaturated alcohols

The $\text{endo}$ face specific reduction of $\text{endo}$-6-methylenebicyclo[2,2,2]octan-2-ol and $\text{endo}$-6-methy[bicyclo [2,2,2]-oct-5-en-2-ol with D₂ and iridium catalysts is accompanied by deep-seated isotopic redistribution through an intramolecular mechanism, although only two deuterium atoms are incorporated on average. Individual isotopomers of the product may be identified in the ¹³C N.m.r. spectrum at 125 MHz. and their ratio is generally consistent with a mechanism in which product is formed by breakdown of an alkyliridium trihydride. Iridium (and rhodium) catalysts part-isomerise the exocyclic olefin to its endocyclic isomer $\text{via}$ an Ir-allyl intermediate without incorporation of deuterium. The reduction of 3-methylcyclohex-2-enol is likewise accompanied by considerable scrambling, with isotopic enrichment occurring at C2, C3, C4 and C5 of the product, $\text{trans}$-3-methylcyclohexanol. Deuteration occurs exclusively on the hydroxyl-bearing face of the molecule.     

Biosynthesis of psilotin from [2′,3′-13C2,1′-14C,4-3H]phenylalanine studied with 13C-NMR

The 6-phenyl-dihydro-α-pyrone moiety of psilotin is formed from [2′,3′-¹³C₂,1′-¹⁴C,-4-³H]phenylalanine in the plant $\text{Psilotum}$$\text{nudum}$ with retention of all the isotopes.