Showing papers on "Pyran published in 1988"
35 citations
Journal Article•
TL;DR: Synthese et etude biologique d'[aryl oxy imino]-7 dimethyl-5,5 tetrahydro-3,5,6,7 furo [3,4-b] pyrannones-3
Abstract: Synthese et etude biologique d'[aryl oxy imino]-7 dimethyl-5,5 tetrahydro-3,5,6,7 furo [3,4-b] pyrannones-3
32 citations
TL;DR: Isomeric 6- and 9-hydroxy-naphtho-z.sfnc;2,3-bz;pyran-5,10-quinones were synthesised by alkylation-cyclization of 2- and 3-hydroxjuglone in a single step and can be distinguished by UV-visible spectra in the presence of additives and 1 HNMR as discussed by the authors.
27 citations
TL;DR: Methyl acetoacetate and 2,4-pentanedione dianions were condensed with aldehydes and ketones to afford a 1,3,5-trioxygenated carboskeleton as discussed by the authors.
27 citations
27 citations
TL;DR: Preparation du compose du titre a partir du tri-O-benzoyl-2',3,5' β-D-ribofuranosyl-5 furfural et traitement par differentes amines.
Abstract: Preparation du compose du titre a partir du tri-O-benzoyl-«2',3',5' β-D-ribofuranosyl-5 furfural et traitement par differentes amines
25 citations
22 citations
TL;DR: The cycloaddition of dihydropyran to benzylideneaniline and to other anils gives tetrahydroquinolines resulting from [4 + 2] addition; contrary to a recent report, there is no evidence for the formation of [2+ 2] adducts as mentioned in this paper.
18 citations
TL;DR: A series of substituted 5,11-dihydro[1]benzoxepino[3,4-b]pyridines was synthesized and evaluated for antiulcer activity in water immersion/restrained stress ulcer assay in rats and showed weak antisecretory activity in pylorus-ligated rats.
Abstract: A series of substituted 5,11-dihydro[1]benzoxepino[3,4-b]pyridines was synthesized and evaluated for antiulcer activity in water immersion/restrained stress ulcer assay in rats. Structure-activity relationships are described. Most of the tested compounds exhibited low affinity to the muscarinic acetylcholine receptor. The molecular features for the best activities are the 2-(diethylamino)ethylenediamine group at the 5-position of the oxepin ring and an oxepin skeleton rather than a thiepin or a pyran skeleton. Methyl and chlorine substitution on the benzene ring reduced the activity. Compound 11, 5-[[2-(diethylamino)ethyl]amino]-5,11-dihydro[1]benzoxepino [3,4-b]pyridine trihydrochloride was selected for further evaluation. Synthesis and antiulcer activity of optically active 11 is described. There were no statistically significant differences between (+)-, (-)-, and (+/-)-11. Compound 11 showed weak antisecretory activity in pylorus-ligated rats. It is now under clinical evaluation as KW 5805.
17 citations
TL;DR: Dimethyl acetonedicarboxylate formed the enamine with benzylamine and thereby converted one of the carbomethoxy groups into a less electrophilic vinylogous urethane as discussed by the authors.
15 citations
TL;DR: In this paper, the authors describe the vinylation of composes du titre se fait par des [cyano divinyl] cuivre-dilithium; la dihydro-3,4 trimethyl-2,2,6 pyrannone-4 ne conduit pas au produit d'addition 1,2 ou 1,4 mais a l'hydroxy-4 methyl-6 heptadiene-3.5one-2
Abstract: La vinylation des composes du titre se fait par des [cyano divinyl] cuivre-dilithium; la dihydro-3,4 trimethyl-2,2,6 pyrannone-4 ne conduit pas au produit d'addition 1,2 ou 1,4 mais a l'hydroxy-4 methyl-6 heptadiene-3,5one-2
TL;DR: The thermal decomposition of isochroman-3-one to benzocyclobutene and carbon dioxide, of benzyl methyl ether and 2-hydroxyethylbenzene to toluene and formaldehyde, and of phenyl acetate to phenol and ketene are each first-order unimolecular reactions as discussed by the authors.
Abstract: The thermal decomposition of isochroman-3-one to benzocyclobutene and carbon dioxide, of benzyl methyl ether and 2-hydroxyethylbenzene to toluene and formaldehyde, and of phenyl acetate to phenol and ketene are each first-order unimolecular reactions. The Arrhenius parameters [E/kJ mol–1, log (A/s–1)] are 221.1, 14.305; 231.7, 12.92; 200.5, 11.21; and 221.8, 11.78, respectively. The frequency factors indicate that each reaction involves a cyclic semi-concerted mechanism; for phenyl acetate this is a four-centre process analogous to that involved in the formation of ketene from pyrolysis of either acetic acid, acetyl bromide, or acetamide. The higher log (A/s–1) value for isochroman-3-one is typical of elimination from cyclic compounds, because their ground states are already constrained into the geometry required in the transition state. Chroman-1-one (dihydrocoumarin) is very much more stable than isochroman-3-one (and on decomposition gives mainly coumarin and benzo[b]furan, evidently due to the favourable gain in aromaticity). Decomposition of 3,4-dihydro-2H-pyran into ethene and propenal takes place according to the rate equation log k= 13.556 – 209.01/19.142 K, the rate coefficients being lower than the literature values which may therefore have been affected by surface catalysis. A 2-methyl group in the pyran produces a ca. 4.5-fold rate acceleration, very similar to that produced in the analogous vinyl ethers. The relationship between the elimination rates for a range of cyclic compounds and their open-chain counterparts is examined and it is found that their reactivities are closely similar. Hydrogen is shown to be transferred as an incipient anion in allyl ether pyrolysis, whereas in most eliminations it is transferred as an incipient cation.
TL;DR: The pyranonaphthoquinones of levoglucosenone (1,6-anhydro-3,4-dideoxy-β- d - glycero -hex-3-enopyranos-2-ulose) with zinc under ultrasonic irradiation gave 53% of the exo -adduct (1 S,3 R,4a R,10a S )-3 11-anh-hydroxy-1-hydroxymethyl-4-oxo-3.4,5,10
TL;DR: A modified Strecker reaction on tetrahydro-2H-pyran-3-one derivatives yielded α-benzylamino nitriles, which upon subsequent hydrogenation and hydrogenolysis gave the target 1,2-diamines.
TL;DR: The structure and stereochemistry of (4aS,7S, 7aR)-nepetalactam isolated from a commercial sample of catnip oil, were established by spectroscopic studies and by conversion to δ-skytanthine and to known compounds derived from nepetalic acid.
Abstract: The structure and stereochemistry of (4aS,7S,7aR)-nepetalactam isolated from a commercial sample of catnip oil, were established by spectroscopic studies and by conversion to δ-skytanthine and to known compounds derived from nepetalic acid and nepetalactone
TL;DR: In this paper, a number of quinones were converted to the title quinone using base-induced cyclization. But the conversion was performed in the presence of base-specific base-induced cyclisation.
Abstract: 3-Acetyl-5-methoxy-1,7-bisisopropoxy-4-naphthol (11) was converted in a number of high yielding transformations into the title quinones. Key steps were the stereospecific base-induced cyclisation in almost quantitative yield of 2-allyl-4,7-bisbenzyloxy-3-(1-hydroxyethyl)-1,5-dimethoxynaphthalene (18) into 7,10-bisbenzyloxy-3,4-dihydro-5,9-dimethoxy-trans-dimethyl-1H-naphtho[2,3-c]pyran (20) followed by the oxygenation of (20) to afford its two C-4 hydroxy epimers (23) and (26) in high combined yield, by potassium t-butoxide in dimethyl sulphoxide in the presence of oxygen. The efficient conversion of the major pseudoequatorial hydroxy compound (23) into the minor pseudoaxial hydroxy epimer (26)via the corresponding pseudoaxial chloro derivative was useful in providing increased quantities of precursors to quinone A′.
TL;DR: In this paper, a highly stereoselective synthesis of a cis-pyrano[2, 3-b]pyran has been developed utilizing a BF 3 ·OEt 2 catalyzed glycosidation reaction of activated glycals with 1-hydroxy-2-propenyltrimethylsilane.
TL;DR: In this paper, 3-Aryl-4-(1-phenyl-1H-pyrazol-4-yl) coumarins and 3,4-diarylcoumarins (5) were synthesised by reaction of 1phenyl 4-(2′-hydroxybenzoyl) pyrazoles (1) and 2-hydroxbenzophenone (2) respectively with arylacetyl chlorides (3) under Phase Transfer Catalysis conditions.
Patent•
09 Nov 1988
TL;DR: In this paper, the disclosed compounds of the formula, where n is 0 or 1, and m is 1 or 2, are shown to be antipsychotic, analgesic, anticonvulsant and anxiolytic agents.
Abstract: There are disclosed compounds of the formula, where n is 0 or 1; A is where X, Y, Z, U, V, W, Q, S and T are each hydrogen, halogen, loweralkyl, hydroxy, nitro, loweralkoxy, amino, cyano or trifluoromethyl; m is 1 or 2; R₁ and R₂ are independently hydrogen, loweralkyl or aryl, or alternatively R₁ + R₂ taken together with the carbon atom to which they are attached form a cyclopentane, cyclohexane, cycloheptane, pyran, thiopyran, pyrrolidine or piperidine ring; R₃ and R₄ are independently hydrogen or loweralkyl, or alternatively R₃ + R₄ taken together with the carbon atom to which they are attached form a cyclopentane, cyclohexane, cycloheptane, pyran, thiopyran, pyrrolidine or piperidine ring, the term aryl signifying an unsubstituted phenyl group or a phenyl group substituted with 1, 2 or 3 substituents each of which being independently loweralkyl, loweralkoxy, hydroxy, halogen, loweralkylthio, cyano, amino or trifluormethyl, and a process for their preparation. The compounds are useful as antipsychotic, analgesic, anticonvulsant and anxiolytic agents.
TL;DR: In this article, three-step synthesises of cyclopenta[C]pyran and its 6-tert-butyl derivative are described, and the 1H-NMR, 13C-NMs, and electronic spectra of the lemon-yellow isooxalenes are compared with those of other pseudoazulenes.
TL;DR: The structural and spectral properties of a pyran ring containing an enaminoester moiety are described in this paper, and the results indicate an almost planar heterocyclic ring and a complex hydrogen bonding situation.
TL;DR: In this article, the aroylketene S,N-acetals 1a-j were shown to undergo regioselective conjugate 1,4-addition with Reformatsky reagent derived from ethyl bromoacetate, followed by cyclization to give novel 4-amino-6-aryl-2H-pyran-2-ones 3a.
Abstract: The aroylketene S,N-acetals 1a-j are shown to undergo regioselective conjugate 1,4-addition with Reformatsky reagent derived from ethyl bromoacetate, followed by cyclization to give novel 4-amino-6-aryl-2H-pyran-2-ones 3a-j in good yields.
TL;DR: In this article, a Diels-Alder reaction of methyl 2-oxo-2H-pyran-5-carboxylate (1) with isoprene gave two stereoisomers, methyl 8-methyl-8-vinyl- and 8-isopropenyl-3-oxosmide-2-oxabicyclo[2.2]
Abstract: A Diels–Alder reaction of methyl 2-oxo-2H-pyran-5-carboxylate (1) with isoprene gave two stereoisomers, methyl 8-methyl-8-vinyl- and 8-isopropenyl-3-oxo-2-oxabicyclo[2.2.2]oct-5-ene-6-carboxylates....
TL;DR: In this paper, a method to synthesize naphtho[2,3-c]pyran-5,10-quinones was described. But this method was performed without perturbation of the pyran ring stereochemistry; this was confirmed by an X-ray crystallographic investigation.
Abstract: A route is described to 1,5,7-trialkoxy-4-naphthols. A method has been established to convert these compounds into the corresponding 3-acetyl-4-naphthols, in good yield, with a view to synthesizing naturally derived naphtho[2,3-c]pyran-5,10-quinones. Boron trichloride-induced monodemethylation of racemic Quinone A dimethyl ether was effected without perturbation of the pyran ring stereochemistry; this was confirmed by an X-ray crystallographic investigation.
TL;DR: Oxymercuration of (R)-sulcatol (1) to (3R,6R)-2 was followed by its treatment with NaBH4 and oxygen to give (3S, 6R)-tetrahydro-2,2,6-trimethyl-2H-pyran-3-ol (3a) and (3 R, 6S)-3a′.
TL;DR: In this paper, a peri-heterocyclization of 8-hydroxy-1-naphthaldehydes with an active methylene compound in the presence of potassium carbonate is presented.
TL;DR: In this article, the role played by cation radicals in these reactions is discussed, related to the 1H nmr line broadening phenomena observed earlier, and explained in terms of a slight preferential concentration of unpaired spin at position 5 of a cation-radical derived from 6-hydroxychroman.
Patent•
12 Jan 1988
TL;DR: In this article, the authors defined a class of terocyclic derivatives of tetrahydro(thio)pyran-2,4-dione derivatives of the formula ##STR1##, where R 1 is hydrogen, a cation, alkyl carbonyl, C 2 -C 10 -alkenylcarbonyl or benzoyl which is unsubstituted or substituted by alkyls, R 2 is alkyyl, R 3 is a non-aromatic, unsubstitized or alky-substit
Abstract: Tetrahydro(thio)pyran-2,4-dione derivatives of the formula ##STR1## where R 1 is hydrogen, a cation, alkylcarbonyl, C 2 -C 10 -alkenylcarbonyl, or benzoyl which is unsubstituted or substituted by alkyl, R 2 is alkyl, R 3 is a non-aromatic, unsubstituted or alkyl-substituted heterocyclic compound of 5 to 7 ring members and having at most one double bond in the heterocyclic ring, X is oxygen or sulfur, and Z is oxygen or the radical NO--R 4 , R 4 denoting alkyl, alkenyl, alkynyl, haloalkyl, hal oalkenyl, alkoxyalkyl or the radical CH 2 --R 5 , where R 5 is a he terocyclic compound of 5 ring members and containing from 1 to 3 hetero-atoms and from 0 to 2 double bonds and bearing either no substituents or one or two substituents selected from the group consisting of alkyl, alkoxy, halogen, trifluoromethyl, alkoxymethyl, alkylthiomethyl and vinyl, or R 5 is phenyl which is unsubstituted or bears from one to three substituents selected from the group consisting of alkyl, alkoxy, halogen, trifluoromethyl, nitro and dialkylamino, and their use for combating unwanted plant growth and for regulating plant growth.
Patent•
01 Jun 1988
TL;DR: Substituted benzoyl - 2H - pyran - 3,5 - (4H, 6H) - diones and related compounds as discussed by the authors and the use of said compounds for the control of weeds.
Abstract: Substituted benzoyl - 2H - pyran - 3,5 - (4H, 6H) - diones and related compounds (including their enol ethers and corresponding thiopyran and piperidine diones) and the use of said compounds for the control of weeds.