An efficient HCCP-mediated direct amination of quinazolin-4(3H)-ones

An efficient direct amination of quinazolin-4(3H)-ones has been developed. Treatment of quinazolin-4(3H)-ones with HCCP, DIPEA, and N-contained nucleophiles in acetonitrile could be able to form the corresponding 4-aminoquinazoline derivatives. Under the optimal reaction conditions, the amination products were achieved in good yields.     

An efficient synthesis of 4,5-dihydronaphtho[2,1-b]furan through a novel ring transformation of 2H-pyran-2-one

An innovative route for the synthesis of substituted naphtho[2,1-b]furan has been delineated through a ring transformation reaction of suitably functionalized 2H-pyran-2-ones by reaction with 6,7-dihydro-5H-benzofuran-4-one, in good yield.     

Efficient synthesis of 6-aryl-4-trifluoromethyl/ethoxycarbonyl-2H-pyran-2-ones through self-condensation of penta-2,4-dienenitriles

An efficient synthesis of two new series of 6-aryl-4-trifluoromethyl-2H-pyran-2-ones and 6-aryl-4-carboxyethyl-2H-pyran-2-ones, obtained through the self-condensation reaction of 5-aryl-5-methoxy-3-(trifluoromethyl)penta-2,4-dienenitriles 3 and ethyl 4-aryl-2-(cyanomethylene)-4-methoxybut-3-enoates 4 respectively, is reported. The self-condensation reaction of the enoates 4 was performed in water in the presence of hydrochloric acid whereas the self-condensation reaction of the penta-2,4-dienenitriles 3 required the use of zinc bromide and hydrochloric acid in order to give the respective 2H-pyran-2-ones. Products were obtained up to 97% yield.     

An efficient synthesis of 4H,5H-pyrano[3,4-c]pyran-4,5-diones from a suitably functionalized 2H-pyran-2-one

An efficient synthesis of ethyl 7-aryl-2-methyl-4H,5H-pyrano[3,4-c]pyran-4,5-dione-1-carboxylate 5, and ethyl 6-aryl-3-cyano-2H-pyran-2-one-4-acetate 6 has been delineated by reaction of suitably functionalized 2H-pyran-2-ones 1 with ethyl acetoacetate 2.     

Indium-mediated regioselective mono-allylation of 1,5-dicarbonyl compounds and dehydrative cyclization to 2,3-dihydro-4H-pyran-4-ones and 3,4-dihydro-2H-[1,4]oxazines

An indium-mediated Barbier type mono-allylation of 1,5-dicarbonyl compounds and a subsequent acid-catalyzed dehydrative cyclization afforded 2,3-dihydro-4H-pyran-4-ones and 3,4-dihydro-2H-[1,4]oxazines.     

Iminofuran chemistry: VII. Intramolecular cyclization of 2-N-aryl-substituted derivatives of 2-amino-4-aryl-4-oxobut-2-enoic and 2-amino-5,5-dimethyl4-oxohex-2-enoic acids

The cyclization at the treatment of acetic anhydride of 4-aryl-2-arylamino-4-oxobut-2-enoic and 2-arylamino-5,5-dimethyl-4-oxohex-2-enoic acids was investigated furnishing derivatives of 5-aryl-3-aryl-imino-3H-furan-2-ones and 4-arylamino-2-tert-butyl-2,5-dihydro-5-oxofuran-2-yl acetate respectively. 2-N²-Methylenesubstituted 4-aryl-2-hydrazino-4-oxobut-2-enoic and 5,5-dimethyl-2-hydrazino-4-oxohex-2-enoic acids cleanly underwent cyclization under the effect of acetic anhydride into 5-aryl-3-hydrazono-3H-furan-2-ones and 5-tert-butyl-3-hydrazono-3H-furan-2-ones.     

3-methylthio-1,2-dithiolylium salts : Reaction with 4-hydroxy-6-methyl-2H-pyran-2-one and 4-hydroxycoumarin

The reaction of 4- and 5-aryl-3-methylthio-1,2-dithiolylium iodides with 4-hydroxy-6-methyl-2$\text{H}$-pyran-2-one and 4-hydroxycoumarin has been studied. 4-Substituted salts yielded 3-aryl-7-methyl-2-thioxo-2$\text{H}$,5$\text{H}$-pyrano [3,2-c]pyran-5-ones and 3-aryl-2-thioxo-2H,5H-pyrano[3,2-c]benzo[e]pyran-5-ones, respectively, whereas 5-substituted salts gave rise to 3-(5′-aryl-1′,2′-dithiol-3′-ylidene)-6-methyl-2$\text{H}$-pyran-2,4-diones and 3-(5′-aryl-1′,2′-dithiol-3′-ylidene)-2$\text{H}$-benzo [b]-pyran-2,4-diones.     

ReBr(CO)5-catalyzed sequential addition-cyclization of 1,3-dicarbonyl compounds with electron-deficient internal alkynes affording trisubstituted 2H-pyran-2-ones

The reaction of 1,3-dicarbonyl compounds such as acetoacetate, acetylacetone, dibenzoylmethane, and benzoylacetate with electron-deficient internal alkynes in the presence of catalytic amount of ReBr(CO)₅ in toluene under neutral conditions resulted in the formation of 4,5,6-trisubstituted 2H-pyran-2-ones in moderate to high yield. The reaction took place via a two-step sequence including the rhenium(I)-catalyzed addition of the activated methylenes to alkynes to give enolic 2-alkenyl derivatives, and subsequently dealcoholic cyclization to form 2H-pyran-2-one derivatives.     

Regioselective synthesis of functionalized naphtho[b]thiophenes through a ‘lactone methodology’

Benzo[b]thiophene and its benzannulated derivatives are important classes of compounds due to their unique chemical properties and biosteric relationship with indole. In this letter, we report a convenient route for the synthesis of substituted naphtho[b]thiophenes through a ring transformation reaction of suitably functionalized 2H-pyran-2-ones with 6,7-dihydro-5H-benzothiophene-4-one, in good yields.     

Synthesis of 6-aryl- and 5-aroylcomanic acids from 5-aroyl-2-carbethoxy-4-pyrones via a deformylative rearrangement and ring-opening/ring-closure sequence

The reaction of 1-aryl-2-(dimethylaminomethylene)butane-1,3-diones with diethyl oxalate in the presence of sodium hydride in THF gave ethyl 5-aroyl-4-oxo-4H-pyran-2-carboxylates, from which 4-oxo-6-aryl-4H-pyran-2-carboxylic acids (6-arylcomanic acids) were obtained in high yields via acid-catalyzed deformylative rearrangement. 5-Aroyl-4-oxo-4H-pyran-2-carboxylic acids (5-aroylcomanic acids) were prepared via а ring-opening/ring-closure sequence by the reaction of 5-aroyl-2-carbethoxy-4-pyrones with piperidine and subsequent basic hydrolysis and acidification.     

Substituent dependent regioselective synthesis of pyranopyrandiones and 1,2-teraryls from 2H-pyran-2-ones

The one-pot substituent-directed regioselective synthesis of 1,7-diaryl-2-methyl-4H,5H-pyrano[3,4-c]pyran-4,5-diones 3 as the major and 3,4-diaryl-2-methyl-6-methylsulfanylbenzonitriles 4 as the minor products has been delineated through ring transformation of suitably functionalized 2H-pyran-2-ones 1 with aryl acetones 2. Under similar reaction conditions, 6-aryl-4-sec-amino-2H-pyran-2-ones 5 led, regioselectively, to 3,4-diaryl-2-methyl-6-sec-aminobenzonitriles 6.     

Regioselective synthesis of 2-amino-isophthalonitriles through a ring transformation strategy

An expeditious synthesis of several 2-amino-isophthalonitriles and their biaryl compounds is described and illustrated by carbanion-induced ring transformation of functionalized 2H-pyran-2-ones with malononitrile in excellent yields. The strength of the reaction lies in the creation of an aromatic ring at room temperature from six-membered lactones under mild reaction conditions. This approach is an alternative to Diels-Alder reactions of 2H-pyran-2-ones with dienophiles, which require forcing thermal conditions to obtain benzene derivatives.     

Synthesis of bridgedhead azolo[3,2-a]pyrimidines and imidazo[2,1-b]thiazines through ring transformation of 2H-pyran-2-ones

Suitably functionalized 3-carbomethoxy/cyano-2H-pyran-2-ones are excellent synthons for the synthesis of arenes and heteroarenes of therapeutic importance. The compounds 6-aryl-3-cyano-4-methylsulfanyl-2H-pyran-2-ones have been transformed into bridgedhead azolopyrimidines and imidazothiazines through thermal and base-induced ring transformation reactions with aminoazoles and imidazolidin-2-thiones, respectively.     

An improved synthesis and some reactions of diethyl 4-oxo-4H-pyran-2,5-dicarboxylate

The reaction of ethyl 2-(dimethylamino)methylene-3-oxobutanoate with diethyl oxalate in the presence of sodium hydride in THF gave diethyl 4-oxo-4H-pyran-2,5-dicarboxylate, from which 4-oxo-4H-pyran-2,5-dicarboxylic and 4-oxo-1-phenyl-1,4-dihydropyridine-2,5-dicarboxylic acids and their derivatives were obtained in good yields.     

Efficient domino strategy for synthesis of 3-substituted 1,5-dihydro-4H-pyrrolo[3,2-c]pyridin-4-one derivatives

A series of 1,5-dihydro-4H-pyrrolo[3,2-c]pyridin-4-one derivatives with 3-(4-hydroxy-2-oxo-2H-pyran-3-yl) groups were synthesized via a one-pot three-component reaction of 4-aminopyridin-2(1H)-ones, 2,2-dihydroxy-1-arylethan-1-ones, and 4-hydroxy-2H-pyran-2-ones in water. This strategy not only provides a valuable tool in the design and synthesis of new hydrogenated pyrrolo[3,2-c]pyridines but also has the advantages of inexpensive starting materials, atom and step economy, environmental friendliness, good to excellent yields, and operational simplicity. A total of 14 examples were examined to show a broad substrate scope and high yields.     

Synthesis of acetylenic β-diketones and their conversion into 4H-pyran-4-ones,pyrazoles, and 1-hydroxy-4-pyridones

A simple method for the synthesis of acetylenic β-diketones is described. They can be cyclized to the corresponding 4H-pyran-4-ones with acids. Their reaction with hydrazine hydrate gave pyrazole derivatives isomeric with those obtained from 4H-pyran-4-ones. With hydroxyl-amine hydrochloride in ethanol, 1-hydroxy-4-pyridones are formed.     

The synthesis of 5-substituted 3-benzoylamino-6-(2-substituted amino-1-ethenyl)-2H-pyran-2-ones and their transformations into 2H-pyrano[3,2-c]pyridine derivatives

A new approach to the 2H-pyrano[3,2-c]pyridine system is described. 5,6-Disubstituted 3-benzoylamino-2H-pyran-2-ones 3a,b , prepared from the corresponding 1,3-dicarbonyl compounds 1a,b and methyl (Z)-2-benzoylamino-3-dimethylaminopropenoate ( 2 ), were converted into 3-benzoylamino-6-(2-dimethylamino-1-ethenyl)-5-ethoxycarbonyl-2H-pyran-2-one ( 4a ) and 5-acetyl derivative 4b . The exchange of the dimethylamino group in 4a,b with aromatic amines 5a-f,m , héteroaromatic amines 5g-i , and benzylamines 5j-l produced 5-ethoxycarbonyl-3-benzoylamino-6-(2-arylamino- or heteroarylamino-or benzylamino-1-ethenyl)-2H-pyran-2-ones 6a-l , and its 5-acetyl analog 6m . The compounds 6 were cyclized in basic media into 2H-pyrano[3,2-c]pyridine derivatives 7a-h . Analogously react also α-amino acid derivatives 8a-c and 11 as nitrogen nucleophiles producing 9a-c, 10 and 12 .     

Hydroalkylation leading to heterocyclic compounds. Part 1: New strategies for the synthesis of polysubstituted 2H-pyran-2-ones

Polysubstituted 2H-pyran-2-ones and 5,6-dihydro-2H-pyran-2-ones were synthesized via the MCRs initiated by the hydroalkylation of alkynoates with activated methylenes. Under the optimized reaction conditions, the desired products were obtained in 47-88% isolated yields. The experimental results showed that the groups on activated methylenes act important roles in the nucleophilic attack fashion.     

A convenient and mild synthesis of new 2-aryl-3-hydroxy-6,7-dihydro-1H-indol-4(5H)-ones via a one-pot,three-component reaction in water

A simple and convenient synthesis of 2-aryl-3-hydroxy-6,7-dihydro-1H-indol-4(5H)-ones is achieved in high yields via the one-pot, three-component reaction of arylglyoxals, 1,3-cyclohexanedione, and ammonium acetate in water under reflux conditions.     

An innovative synthesis of dibenzofurans through a carbanion-induced ring transformation reaction

An innovative route for the synthesis of substituted dibenzofurans has been delineated through a ring transformation reaction of suitably functionalized 2H-pyran-2-ones by reaction with 7-methoxybenzofuran-3-one, in high yield. The novelty of the procedure lies in the creation of an aromatic ring from a 2H-pyran-2-one involving the -COCH₂-moiety of the substrate.