Pyrano pyran-2,5-dione

Pyrano[4,3-6]pyran-2,5-dione, 7-methyl-aromaticity, 3, 639 Pyranopyrandiones aromaticity, 3, 639 dipole moments, 3, 627 synthesis, 3, 795 tautomerism, 3, 644 Pyranopyranones molecular structure, 3, 624 Pyranopyrans synthesis, 3, 760, 784 Pyranopyrazoles synthesis, 5, 321, 330 Pyranopyrazolones synthesis, 5, 334 Pyranopyridine synthesis, 3, 834 Pyranoses... 

Furopyranopyrandiones have been prepared by the cerium(iv) ammonium nitrate-mediated reaction of 4-hydroxy-277,577-pyrano[4,3- ]pyran-2,5-diones with alkenes (Scheme 14) <2003H(60)939>. 

Carbanion-induced ring transformations of pyran-2-ones include their conversion into unsymmetrical biaryls <07TL7283>, axially chiral quateraryls <07JOC7765>, 2-amino-isophthalonitriles <07T10971>, arylated indans <07T10300> and pyrano[3,4-c]pyran-l,8-diones <07TL8998>. 

Step 8 pyrano-, piperidino-, and thiopyrano-derivatives of 2H-pyran-3,5(4H,6H)-dione have been prepared and are described (1). 

Naphthyridin-2(1 //)-ones 66 were prepared from pyrano[4,3-/ ]pyridine-2,7-diones 67 by successive treatment with NH3, HBr and Zn in acetic acid (1993H1). It was believed that the attack of the ammonia molecule on the C(5) atom led to pyran ring opening. Subsequent decarboxylation afforded a tautomeric mixture of substituted tetrahydropyridines 68a,b. Dinitrile 69 generated by elimination of ammonia underwent cyclization under the action of HBr to form 1,6-naphthyridine derivative 70. Dehydrobromination with Zn in acetic acid gave the final products 66. 

Synthesis.—Application of the Kostanecki-Robinson reaction to 3-acyl-4-hydroxy-2//-pyran-2-one gave a mixture of pyrano[4,3-6]pyran-4,5-diones... 

However, when 36 was heated with a-amino heterocycles or with cyclic 1,3-dicarbonyl or potential 1,3-dicarbonyl compounds, 3-heteroarylp)rr-azol derivatives were obtained. In this manner 36 afforded, when heated with 2-aminopyridine and 3-amino-lH-pyrazol in acetic acid under reflux for 2 h and 5 h, respectively, 3-(5-ethoxy-l-phenyl-lH-pyrazol-3-yl)-4H-pyrido[l,2-fl]pyrimid-4-one (38) and 6-(5-ethoxy-l-phenyl-lH-p5rrazol-3-yl)pyrazolo[l,5-fl]pyrimid-7(lH)-one (39) in 70% and 77% 5deld, respectively. Similarly, 36 afforded with cyclicjS-dicarbonyl compounds, such as 4-hydroxy-6-methyl-2H-pyran-2-one and 5,5-dimethylcyclohexane-l,3-dione by heating in acetic acid for 4 h and 8 h, respectively, the corresponding 3-(5-ethoxy-l-phenyl-lH-pyrazol-3-yl)-7-methyl-2H,5H-pyrano[4,3- 7]pyran-2,5-dione (40) and 3-(5-ethoxy-l-phenyl-IH-pyrazol-3-yl)-7,7-dimethyl-7,8-dihydro-2H-chromene-2,5-dione (41) in 26% and 82% yield, respectively (Scheme 15). 

Pyrimidines 73 with dinucleophiles, such as 2-amino-pyridine, 1,3-dimethylbarbituric acid, 5,5-dimethylcyclohexa-l,3-dione and 4-hydroxy-6-methyl-pyran-2(lH)-one, were carried out in boiling acetic acid formed 4H-pyrido[l,2-fl]pyrimidin-4-one (76), lH-pyrano[2,3-d]pyrimidine-2,4,7(3H)-trione (77), 6H-chromene-2,5-dione (78) and pyrano[4,5-b]pyran-2,5-dione (79) in 30%, 67%, 56% and 73% yields, respectively (Scheme 26). 

Hydroxy-6-propenyl-2-pyrone heated 3 hrs. at 100° with crotonoyl diloride in tetrachlorethane in the presence of TiCl4 3,4-dihydro-2-methyl-7-propenyl-2H,5H-pyrano[4,3-b]pyran-4,5-dione. Y 70%. K. Kato, Y. Hirata, and S. Yama-mura, Chem. Commun. 1969, 95. 

Hydroxy-6-methyl-2-pyrone and NaH added to dioxane, refluxed 1 hr., acryloyl diloride in dioxane added dropwise with stirring, and refluxed 7 hrs. 3,4-di-hydro-7-methyl-2H,5H-pyrano[4,3-b]pyran-2,5-dione. Y 84%. F. e., also enolester formation without cyclization, s. B. M. Monroe, J. Heterocyclic Chem. 6, 917 (1969). 

On replacing 2-hydroxynaphthalene-l,4-dione (21) by 4-hydroxy-6-methyl-2H-pyran-2-one (11), Bazgir and his group obtained another series of spiro[indole-3,4 -pyrano[4,3-li]pyran]-3 -carbonitriles (23) under the same reaction conditions they even synthesized these scaffolds using magnetically recoverable and reusable CuFe204 nanoparticles as well in aqueous media (Scheme 12) [112,113], Besides, sodium stearate was also efficiently used in S5mthesiz-ing this spirooxindole scaffold in aqueous micellar media [114],... 

Hydroxy-6- hydroxymethyl)-4-oxo-4W-pyran-2-yl -6- hydroxymethyl)pyrano[3,2-b]pyran-4,8-dione, 9CI [1047-14-9]... 

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