Synthesis of 2-Methyl-9-oxo-9H-furo[2,3-c]benzopyrans and 2-Methyl-3H,4H[1]benzopyrano[3,4-b]pyrrol-4-ones

3:4-Fused furocoumarins and pyrrolocoumarins are synthesised from 3-hydroxy and 3-benzamido-substituted coumarins by a novel two step sequence.     

Synthesis of 2-Methyl-3-acetyl-5-oxo-5H-[1]benzopyrano[2,3-b]pyridine

For our synthetic work we needed the title compound. Literature survey revealed that 2-amino-4-oxo-4H-[1] benzopyran-3-carboxaldehyde (2-amino-3-formylchro-mone) can undergo condensation with diethyl malonate (or ethyl cyanoacetate) forming ethyl 2-hydroxy(or amino)-5-oxo-5H-[1]benzopyrano[2,3-b]pyridine-3-carboxylate¹.     

Synthesis of 5H-[1]benzopyrano[4,3-b]pyridin-5-ones containing an azacannabinoidal structure

Starting from 7-alkoxy-4-aminocoumarins 5,6,8,12 , and 13 as key intermediates, this paper describes two different methods for the preparation of azacannabinoidal 5H[1]benzopyrano[4,3-b]pyridin-5-ones 24–27, 38 , and 39 containing typical structural requirements for ZNS activity. First, Michael addition of 6 and 8 to the double bonds of alkyl vinyl ketones 14 and 15 resulted in a mixture of tetrahydropyridines 24–27 and fused pyridines 20–23 the latter of which were reduced by sodium cyanoborohydride to give the target compounds 24–27 . The second, pyridine ring closure was accomplished by a combination of Vilsmeier acetylation and formylation resulting in fused 4-chloropyridines 31–33 followed by reduction.     

Synthesis of 2,3,3a,8 a-tetrahydrofuro[2,3-b] benzofuran-2-one from coumarin

4-Vinyl-3,4-dihydrocoumarin, which is obtained in two steps from 3-(2-benzyloxyphenyl)allyl alcohol, was converted to 2,2,3a,8a-tetrahydrofuro[2,3-b]benzofuran-2-one by oxidation and rearrangement.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 748–750, June, 1976.     

Heterocyclic system. XI. Synthesis of 1H,4H-pyrazolo[4,3-b]pyrrolizine and 2H,4H-pyrazolo[4,3-b]pyrrolizine derivatives

Cyclization of pyrrolidinocarboxamide derivatives of 1-phenyl-5-(1H-pyrrol-1-yl)-1H-pyrazole-4-carboxylic acid and 2-phenyl-3-(1H-pyrrol-1-yl)-1H-pyrazole-4-carboxylic acid afforded imminium salts which were transformed into the corresponding ketones. Further reduction of the latter compounds furnished the title derivatives.     

Condensed benzopyrans III. 3H,4H[1] benzopyrano [3,4-b] pyrrol-4-ones

The diazotization of 3-aminocoumarin followed by its reduction gave the cournarin-3-yl-hydrazine which, without isolation, reacted with various carbonyl compounds in a Fisher's indohzation reaction to give derivatives (Ib-Ih) of the yet unreported system 3H,4H[1]benzopyrano[3,4-b]pyrrol-4-one.     

1, 3-dipolar cycloaddition of diazomethane to azolopyridazines. The synthesis of 8-methyl-8H- and 9-methyl-9H-pyrazolo[3, 4-d]-s-triazolo[4, 3-b]pyridazine and 1-methyl-1H- and 2-methyl-2H-imidazo[1, 2-b]pyrazolo[3, 4-b]pyridazine derivatives

The transformations of 7-methyl-7H- and 8-methyl-8H-pyrazolo[4, 3-d]tetrazolo[1, 5-b]pyridazines 1, 2, 9 and 10 into 8-methyl-8H- and 9-methyl-9H-pyrazolo[3, 4-H]-s-triazolo[4, 3-b]pyridazines 7 and 8 , and 1-methyl-1H-and 2-methyl-2H-imidazo[1, 2-b]pyrazolo[3, 4-d]pyridazines 13 and 14 are described.     

Reaction of ketenes with N,N-disubstituted α-aminomethyleneketones VII. Synthesis of 2H,5H-[1]benzothiopyrano[4,3-b]pyran and 2H,5H-thiopyrano[4,3-b]pyran derivatives

The dipolar 1,4-cycloaddition of dichloroketerie to N,N-disubslituled 3-aminomethylene-2,3-dihydro-4-thiochromanones and 3-aminomethylenetelrahydro-4-thiopyranones gave N,N-disubstituted 4-amino-3,3-diehloro-3,4-dihydro-2H,5H-[1]benzolhiopyrano[4,3-b]pyran-2-ones and 4-amino-3,3-dichloro-3,4,7,8-tetrahydro-2H,5H-thiopyrano[4,3-b]pyran-2-ones, respectively, only in the ease of aromatic or strong hindering aliphatic N-substitution. The adducts gave N,N′-disubstituted 4-amino-3-chloro-2H,5H-[1]benzothiopyrano[4,3-b]pyran-2-ones and 4-amino-3-chloro-7,8-dihydro-2H,5H-thiopyrano[4,3-b]pyran-2-ones, respectively, by dehydro-chlorination with DBN. By chromatography on neutral alumina, 3-(2,2-dichloroethylidene)-2,3-dihydro-4-thiochromanone was isolated as an unstable liquid from the reaction between dichloroketerie and 3-diethylaminornethylene-2,3-dihydro-4-thiochromanone.     

Formation of alkyl 6-Aryl-1,7-dioxo-4,4,8-trimethyl-6,9-diphenyl-1H-2,4,6,7,8,9-hexahydrodipyrrole-[3,4-b:4',3',2'-d]quinoline-8-carboxylates

Russian Journal of General Chemistry -     

Regioselective acylation of methyl 2-methyl-4H-thieno[3,2-b]pyrrole-5-carboxylate

The influence of catalysts, acid chlorides, and solvents on the acylation of methyl 2-methyl-4H-thieno[3,2-b]pyrrole-5-carboxylate was studied. The use of AlCl₃ allows the regioselective introduction of the acyl group into position 3 to be performed, whereas the acyl group is regioselectively introduced into position 6 of thienopyrrole when SnCl₄ is used.     

Fused heterocycles. 8 . An efficient procedure for the stereoselective synthesis of trans-2,3,3a,4-tetrahydro-3-aryl-2-phenyl[1]benzopyrano[4,3-c]pyrazoles and their [1]benzothiopyrano analogues

Stereoselective synthesis of trans-2,3,3a,4-tetrahydro-3-aryl-2-phenyl[1]benzopyrano[4,3-c]pyrazoles 13–18 and their [1]benzothiopyrano analogues 19–24 has been performed by the reaction of 3-arylidenechromanones 1–6 and 3-arylidene-1-thiochromanones 7–12 with phenylhydrazine in hot pyridine. The structure and stereochemistry of the compounds prepared have been elucidated by ir, ^lH and ¹³C nmr measurements.     

Formation of alkyl 1-methyl-3,9-dioxo-2-phenyl-2,3,4,9-tetrahydro-1H-pyrrolo[3,4-b]quinoline-1-carboxylates by thermolysis of alkyl 1,5-diaryl-4-methyl-2,3,6-trioxo-1,2,3,4,5,6-hexahydropyrrolo[3,4-b]pyrrole-4-carboxylates

Russian Journal of Organic Chemistry -     

Synthesis of 5-amino-3a,4-dicyano-2,3,3a,6a-tetrahydrofuro[2,3-b]pyrroles

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, p. 282, February, 1992.     

Effect of gastric acidity on bioavailability of N,N-dimethylcarbamoylmethylalpha, 2-dimethyl-5H-[1]benzopyrano[2,3-b]pyridine-7-acetate, a new prodrug-type anti-inflammatory agent

The effect of gastric acidity on the bioavailability of N,N-dimethylcarbamoylmethyl alpha,2-dimethyl-5H-[1]benzopyrano[2,3-b] pyridine-7-acetate (1), a new anti-inflammatory agent, was investigated in gastric acidity-controlled beagle dogs. The dissolution rates of this compound in media of pH 1.2 and 3.0 were greater than those in media of pH 5.0 and 6.8. Reflecting these dissolution characteristics, the peak plasma concentration (Cmax) and the area under the plasma concentration-time curve (AUC0-12h) were reduced by shifting the gastric acidity to low levels (more than pH 6) with omeprazole treatment. In designing dosage forms of 1, it is necessary to develop pharmaceutical preparations whose bioavailability is not affected by the gastric acidity.