Über das 4-Hydroxy-6,6-dimethyl-5,6-dihydro-2(1H)-pyridinthion bzw.-on und die entsprechenden Tautomeren

The tautomers, 4-hydroxy-5,6-dihydro-6,6-dimethyl-2(1H)-pyridinethione (1) and 6,6-dimethyl-2-thioxo-4-piperidone (2) resp., and 4-hydroxy-5,6-dihydro-6,6-dimethyl-2(1H)-pyridone (9) and 6,6-dimethyl-2,4-piperidinedione (10) resp. were synthesized by hydrolysis of 4-amino-5,6-dihydro-6,6-dimethyl-2(1H)-pyridinethiones (4, 5) and-ones (11, 12).1, 2 and9, 10 undergo an aminolysis in amines to the corresponding 4-aminodihydro-2(1H)-pyridinethiones4, 5 and-ones11, 12 resp.

     

Addition-Rearrangement of Aryl- and Alkoxysulfonyl Isocyanates with 5-Methyl-Substituted 3,4-Dihydro-2-methoxy-2H-pyrans. Selective Synthesis of Functionalized 2-Piperidones(1)

3,4-Dihydro-2-methoxy-5-methyl-2H-pyran and 3,4-dihydro-2-methoxy-5,6-dimethyl-2H-pyran undergo addition-rearrangement reactions with arylsulfonyl isocyanates to generate the corresponding 3-formyl- and 3-acetyl-6-methoxy-3-methyl-1-(arylsulfonyl)-2-piperidones. For example, 3,4-dihydro-2-methoxy-5-methyl-2H-pyran and phenylsulfonyl isocyanate afforded 3-formyl-6-methoxy-3-methyl-1-(phenylsulfonyl)-2-piperidone as a separable trans/cis mixture in high yield. The more reactive phenoxysulfonyl and alkoxysulfonyl isocyanates provided analogous results.     

Synthesis of some amino-substituted furanopyrimidines and styrylpyrimidines

5-p-Chlorophenyl-6,6-dimethyl-5,6-dihydro-3H-furano[2,3-d]pyrimidine-4-one is readily converted to 4,6-dichloro-5-β-β-dimethyl-α- (p-chlorostyryl)pyrimidine by warming in phosphorus oxychloride and acetic acid, behavior which is in strong contrast to that of the analogous 5-phenyl derivative. The reaction provides a convenient source of 4-amino-6-chloro-5β,β-dimethyl-α- (p-chlorostyryl)pyrimidines and 4,6-diamino-5-β,β-dimethyl-α- (p-chlorostyryl)pyrimidines, compounds of potential biological interest.     

Regioselective Synthesis of 4-Acetyl-and 5-Acetyl-3-methylisoxazole: Their Conversion into Silyl-and Methyl Enol Ethers

Acetonitrile oxide reacts regioselectively with 3-buten-2-one and (E)-4-methoxy-3-buten-2-one to give 5-acetyl-2 and 4-acetyl-3-methylisoxazole 3, respectively. Treatment of ketones 2 and 3 with trimethylsilyl trifluoromethanesulfonate gave the silyl enol ethers 4 and 5, whereas the methyl enol ethers 8 and 9 were obtained via elimination of methanol from the corresponding dimethyl ketals.     

Synthesis and Photoisomerization of 3-Cyano-6,6-dimethyl-4-(4-nitrophenylvinyl)-5,6-dihydropyran-2-one

The condensation of 4-nitrobenzaldehyde with 3-cyano-4,6,6-trimethyl-5,6-dihydropyran-2-one leads to the formation of a crotonization product and a compound of the Michael adduct type. The main product of the photochemical conversion of (E)-3-cyano-6,6-dimethyl-4-(4-nitrophenylvinyl)-5,6-dihydropyran-2-one is the Z-isomer. Investigation of the photoisomerization of 3-cyano-6,6-dimethyl-4-(4-nitrophenylvinyl)-5,6-dihydropyran-2-one by the semiempirical AM1 method showed that in the ground state the E-isomer was thermodynamically more stable than the E-isomer. E-Z-photoisomerization is effected most probably through the lowest excited singlet state S₁.     

Formation of carbon-carbon single bonds from isocyanates and cyclic pentaoxyphosphoranes—VI : Synthesis of 4-oxazolones and 4-thiazolones,and a new type of chapman rearrangement

The reaction of 4,5-dimethyl-2,2,2-trimethoxy-2,2-dihydro-1,3,2-dioxaphospholene with carbomethoxy, carbopropoxy and N,N-diphenylcarbamyl isocyanates yields, respectively, 2-methoxy-, 2-propoxy- and 2- diphenylamino-5-acetyl-5-methyl-2-oxazolin-4-one. The reaction with carbophenoxy isocyanate gives two products in a proportion which depends on experimental conditions: 2-phenoxy-5-acetyl-5-methyl-2-oxalin-4-one (1:1 stoichiometry) and 1,3-dicarbophenoxy-5-acetyl-5-methyl-hydantoin (1:2 stoichiometry). The 2-substituted 4- oxazolones are hydrolyzed to 5-acetyl-5-methyl-oxazolidin-2,4-dione. The alkyl group of the 2-alkoxy-4-oxazolones migrates to the adjacent nitrogen to give 3-alkyl-5-acetyl-5-methyl-oxazolidin-2,4-diones. The dioxaphospholene reacts with 2-substituted 2-thiazolin-4,5-diones to give 2-substituted 5-acetyl-5-methyl-2-thiazolin-4-ones, including rhodanine derivatives.     

Ruthenium-catalyzed cyclic carbonylation of allenyl alcohols. Selective synthesis of gamma- and delta-lactones

[reaction: see text] Ruthenium complex-catalyzed carbonylation of allenyl alcohols quantitatively gave cyclic carbonyl compounds, gamma- and delta-lactones, in which the hydroxy group of allenyl alcohols participated in the cyclization. A wide variety of allenyl alcohols, such as mono-, di-, and trisubstituted alcohols, can be used in this reaction to produce 3- and 4-substituted gamma-lactones. Similarly, the cyclic carbonylation of 3,4-pentadien-1-ol 10a and 2-methyl-4,5-hexadien-2-ol 11a gave delta-lactones, 5,6-dihydro-3-methyl-2H-pyran-2-one 10b, and 5,6-dihydro-6,6-dimethyl-3-methyl-2H-pyran. 2-one 11b, respectively, in a quantitative yield.     

Thiophene systems. 13. The synthesis of novel thienopyranones

The syntheses and spectral properties of novel dimethyl-substituted thieno[3,2-b]-, [3,4-b]- and [2,3-b]pyran-ones are described. The uv spectra of the three systems are distinctly different as supported by HOMO/LUMO calculations. 5,6-Dihydro-5,5-dimethyl-7H-thieno[3,4-b]pyran-7-one ( 10 ) and 5,6-dihydro-6,6-dimethyl-4H-thieno[2,3-b]pyran-4-one ( 20 ) represent the first members of these thienopyranone ring systems.     

The conformation of t-butyl 2-methoxy-5, 6-dihydro-2 H-pyran-6-carboxylates and 6,6′- disubstituted 2-methoxy-5,6-dihydro-2H-pyran derivatives on the basis of 1H and 13 C NMR spectra

The ¹H and ¹³C NMR spectra of trans- and cis-tert-butyl 2-methoxy-5,6-dihydro-2H-pyran-6-carboxylates (1 and 2) and 6,6′-disubstituted 2-methoxy-5,6-dihydro-2H-pyrans (3-7) have been recorded. HH and CH coupling constants are discussed in terms of the ¹H₆?⁶H₁ conformational equilibrium. It has been found that 1 occurs exclusively in the ¹H₆ conformation, whereas its cis isomer, 2, exists in an equilibrium of both half-chair forms. 6,6′-Disubstituted 2-methoxy-5,6-dihydro-2H-pyrans 3-6 display spectral and conformational behaviour similar to that of 1, whereas 7 resembles 2 in this respect.     

Reaction of 1-methylthio-3,4-dihydroisoquinolines with amines

A study was carried out on the reaction of 1-methylthio-3,4-dihydroisoquinolines with aromatic and aliphatic amines, thiourea, semicarbazide, and thiosemicarbazide. The reactions with anthranilic acid and 2-amino-3-carboethoxy-4,5-dmeurylthiophene give 6,6-dmethyl-5,6-dihydro-8H-isoquino[1,2-blquinazolin-8-one and 6, 6, 9,10-tetramethyl-5,6-dihydro-8H-benzo[i]thieno[2,3-b]quinolizin-8-one, respectively. 1-Semicarbazido-and 1-thiosemicarbazido-3,4-dihydroisoquinolines were shown to undergo thermal elimination of ammonia to give substituted 1, 2, 4-triazolo [3, 4-a]isoquinolin-3-ones and 1, 2, 4-triazolo[3, 4-ajisoquinoline-3-thiones.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 800-806, June, 1996. Original article submitted June 19, 1995; revision submitted March 14, 1996.     

Bildung von 5,6-Dihydro-1,3(4H)-thiazin-4-carbonsäure-estern aus 4-Allyl-1,3-thiazol-5(4H)-onen

Formation of Methyl 5,6-Dihydro-l, 3(4H)-thiazine-4-carboxyiates from 4-Allyl-l, 3-thiazol-5(4H)-ones . The reaction of N-[1-(N, N-dimethylthiocarbamoyl)-1-methyl-3-butenyl]benzamid ( 1 ) with HCl or TsOH in MeCN or toluene yields a mixture of 4-allyl-4-methyl-2-phenyl-1,3-thiazol-5(4H)-one ( 5a ) and allyl 4-methyl-2-phenyl-1,3-thiazol-2-yl sulfide ( 11 ; Scheme 3). Most probably, the corresponding 1,3-oxazol-5(4H)-thiones B are intermediates in this reaction. With HCl in MeOH, 1 is transformed into methyl 5,6-dihydro-4,6-dimethyl-2-phenyl-1,3(4H)-thiazine-4-carboxylate ( 12a ). The same product 12a is formed on treatment of the 1,3-thiazol-5(4H)-one 5a with HCl in MeOH (Scheme 4). It is shown that the latter reaction type is common for 4-allyl-substituted 1,3-thiazol-5(4H)-ones.     

Derivatives of Condensed Thieno[2,3-d]pyrimidines. 15. Synthesis of 2-Substituted 3-Amino-6,6-dimethyl-5,6-dihydro-8H-pyrano[4'3':4,5]thieno[2,3-d]pyrimidin-4-ones

A method has been developed for the preparation of 2-R-substituted 3-amino-6,6-dimethyl-5,6-dihydro-8H-pyrano[4'3':4,5]thieno[2,3-d]pyrimidin-4-ones based on 2-R-amino-3-ethoxycarbonylpyrano[2,3-c]thiophenes. It has been established that their cyclization with hydrazine hydrate requires vigorous conditions.     

Sur l'orientation et les anomalies de l'acetylation des Bz-méthoxy nitro-2 benzofurannes

4-Methoxy-, 5-methoxy- and 7-methoxy-2-nitrobenzofurans have been acetylated via the Friedel-Crafts reaction under the same reaction conditions. 2-Nitrobenzofuran does not undergo acetylation while 6-methoxy-2-nitrobenzofuran only produces decomposition products. As a result of the positive acetylation reactions, 7-acetyl-4-methoxy-, 4-acetyl-5-methoxy- and 4-acetyl-7-methoxy-2-nitrobenzofuran have been prepared. As side products in the acetylation reactions, 4-methoxy-3-(4′-methoxy-2′-nitro-7′-benzofuranyl)-2,3-dihydrobenzofuran-2-one was isolated when 4-methoxy-2-nitrobenzofuran was the starting material and, likewise, when 5-methoxy-2-nitrobenzofuran was the starting material, 3-chloro-5-methoxy-2,3-dihydrobenzofuran-2-one was obtained. Furthermore, 5-methoxy-2-nitrobenzofuran participated in an unexpected chlorination leading to 4-chloro-5-methoxy-2-nitrobenzofuran.     

Three-component reaction of methyl 2,4-dioxo-4-phenylbutanoate and methyl 2,4-dioxopentanoate with aromatic aldehydes and propane-1,2-diamine and chemical properties of the products

The reactions of methyl 2,4-dioxo-4-phenylbutanoate and methyl 2,4-dioxopentanoate with a mixture of an aromatic aldehyde and propane-1,2-diamine, depending on the initial reactant ratio, gave 4-acyl-1-(2-aminopropyl)-5-aryl-3-hydroxy-2,5-dihydro-1H-pyrrol-2-ones and 1,1′-(propane-1,2-diyl)bis(4-acetyl-3-hydroxy-5-phenyl-2,5-dihydro-1H-pyrrol-2-one). Reactions of substituted 1-(2-aminopropyl)-2,5-dihydro-1H-pyrrol-2-ones with aromatic amines and hydrazines were studied, and the structure of one of the products, 5-(2-aminopropyl)-3,4-diphenylpyrrolo[3,4-c]pyrazol-6-one, was proved by X-ray analysis.     

Studies on quinones. Part 25. Synthetic approaches to 6,9-dioxygenated-benzazepinones

The Schmidt and Beckmann rearrangement of 3,4-dihydro-4,4-dimethyl-1(2H)-naphthalenones bearing oxygenated groups at the 5,8-positions, and some of their oximes are reported. Depending upon the structure of the substrates and the reaction conditions 4,5-dihydro-3H-naphth[1,8-cd]isoxazol, benzazepin-2-one and 5,6-dihydro-7H-tetrazolo[1,5-a][2]benzazepine derivatives were generated.     

Synthesis of 5,6-dihydro-8-methoxy-4H-imidazo[4,5,1-ij]quinolines and some related ring systems

Reduction of amides of 8-amino-6-methoxyquinoline over platinum oxide in glacial acetic acid at room temperature affords 2-substituted-5,6-dihydro-8-methoxy-4H-imidazo [4,5,1-ij]-quinolines (I). The method could not be utilized for urea or carbamate derivatives of 8-amino-6-methoxyquinoline. 2-Amino derivatives of I were prepared through the chloro compound obtained from 5,6-dihydro-8-methoxy-4H-imidazo[4,5,1-ij]quinolin-2(1H)-one, (IV). Several related ring systems have also been prepared.     

Synthesis of 4-methylfuro[3′,2′:5,6]benzofuro[3,2-c]pyridine

4-Methylfuro[3′,2′:5,6]benzofuro[3,2-c]pyridine ( 3 ) was synthetized from 2-acetylfuro[3,2-f]benzo[b]furan ( 4 ) or from 2-acetyl-5,6-dihydrofuro[3,2-f]benzo[b]furan ( 10 ). The key step involves a rearrangement-cyclization of azides 6 and 12 to form 4-methylfuro[3′,2′:5,6]benzofuro[3,2-c]pyridin-1(2H) one ( 7 ) and 8,9-dihydro-4-methylfuro[3′,2′:5,6]benzofuro[3,2c]pyridin-1(2H)-one ( 13 ). Introduction of an aminoalkyl chain on carbon 1 was effected by substitution of 1-chloro-4-methylfuro[3′,2′:5,6]benzofuro[3,2-c]pyridine ( 8 ).     

Photochromic dihetarylethenes. 17. Synthesis and photochromic properties of dithienylethenes containing new heterocyclic bridging fragments

Procedures were developed for the synthesis of substituted bis(2,5-dimethyl-3-thienyl)ethenes containing the imidazol-2-one, 1,3-dioxol-2-one, or 1,3-oxazol-2-one fragments as ethene bridges. These compounds were demonstrated to exhibit the photochromic properties. The cyclic forms of some imidazolone and oxazolone photochromes possess high thermal stability. The structure of photochromic 4,5-bis(4-acetyl-2,5-dimethyl-3-thienyl)-3-methyl-2,3-dihydro-1,3-oxazol-2-one was established by X-ray diffraction analysis. The molecule adopts an anti-parallel conformation similar to that of perfluorocyclopentene-bridged dithienylethenes.     

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.     

Synthese des 4-Hydroxy-6,6-dimethyl-5,6-dihydro-2H-thiopyran-2-thions bzw. -ons und der entsprechenden Tautomeren

The tautomers 4-hydroxy-6,6-dimethyl-5,6-dihydro-2H-thiopyran-2-thione (4 a) and 2-mercapto-6,6-dimethyl-5,6-dihydro-4H-thiopyran-4-one (4 b) resp. were synthesized by hydrolysis of 4-amino-5,6-dihydro-2H-thiopyranthiones6,8. On methylation of4 a,b only the S-methyl product7 is formed. Hydrolysis of 4-amino-2-methylthiothiopyranyliden iodides11 leads—depending on the amino group of11—either to the thiopyranone7 or to the 4-imino-thiopyranes12 and to -amino-,,,-unsaturated-methyldithio carboxylates13. On reaction of4 a,b with hydrogenperoxyd the tautomers 4-hydroxy-5,6-dihydro-2H-thiopyran-2-one5 a and 5,6-dihydro-2H-thiopyran-2,4(3H)diones5 b resp. are formed.4 a,b and5 a,b undergo an aminolysis with prim. and sec. amines to the corresponding 4-amino-2H-thiopyran-2-thiones6,8 and -ones10 resp. On heating in alcohols the 4-alkoxy-thiopyrane-2-thiones and -ones9,14 are formed from4 a,b and5 a,b resp.