340830-09-3Relevant academic research and scientific papers
Synthesis and properties of novel 5-(cyclohepta-2′, 4′,6′-trienylidene)pyrimidine-2(1H),4(3H),6(5H)-triones: Methodology for synthesizing cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborates
Naya, Shin-Ichi,Nitta, Makoto
, p. 3709 - 3718 (2007/10/03)
Novel condensation reaction of tropone with N-substituted and N,N′-disubstitued barbituric acids in Ac2O afforded 5-(cyclohepta-2′,4′,6′-trienylidene)pyrimidine-2(1H), 4(3H),6(5H)-trione derivatives (8a-f) in moderate to good yields. The 13C NMR spectral study of 8a-f revealed that the contribution of zwitterionic resonance structures is less important as compared with that of 8,8-dicyanoheptafulvene. The rotational barriers (ΔG?) around the exocyclic double bond of mono-substituted derivatives 8a-c were obtained to be 14.51-15.03kcalmol-1 by the variable temperature 1H NMR measurements. The electrochemical properties of 8a-f were also studied by CV measurement. Upon treatment with DDQ, 8a-c underwent oxidative cyclization to give two products, 7 and 9-substituted cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborates (11a-c·BF4- and 12a-c·BF4-) in various ratios, while that of disubstituted derivatives 8d-f afforded 7,9-disubstituted cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborate (11d-f·BF4-) in good yields. Similarly, preparation of known 5-(1′-oxocycloheptatrien-2′-yl)- pyrimidine-2(1H),4(3H),6(5H)-trione derivatives (14a-d) and novel derivatives 14e,f was carried out. Treatment of 14a-c with aq. HBF4/Ac2O afforded two kinds of novel products 11a-c·BF4- and 12a,c·BF4- in various ratios, respectively, while that of 14d-f afforded 11d-f. The product ratios of 11a-c·BF4- and 12a-c·BF4- observed in two kinds of cyclization reactions were rationalized on the basis of MO calculations of model compounds 20a and 21a. The spectroscopic and electrochemical properties of 11a-f·BF4- and 12a-c·BF4- were studied, and structural characterization of 11c·BF4- based on the X-ray crystal analysis and MO calculation was also performed.
Studies on pyrimidine-annulated heterocycles: Synthesis and function of novel 9-substituted cyclohepta[b]pyrimido[5,4-d]furan-8,10(9H)-diones
Takayasu, Tohru,Mizuta, Yutaka,Nitta, Makoto
, p. 601 - 606 (2007/10/03)
A new short synthesis of 9-substituted cyclohepta[b]pyrimido[5,4-d]furan-8,10(9H)-diones has been accomplished by the reaction of 3-methyl-, 3-butyl-, and 3-phenylbarbituric acids with 2-chlorotropone in an enolate-substitution process and subsequent dehy
