New synthesis, properties, and oxidizing ability of 1,3-dimethyl-5,10-methanocycloundeca[4,5]furo[2,3-d]pyrimidin- 2,4(1,3H)-dionylium tetrafluoroborate

A novel synthesis of 1,3-dimethyl-5,10-methanocycloundeca[4,5]furo[2,3-d]pyrimidin-2,4(1,3H)-dionylium tetrafluoroborate (10(+).BF(4)(-)) was accomplished by the reaction of 3,8-methano[11]annulenone with dimethylbarbituric acid and following acidic cyclization, albeit in low yield. Remarkable structural characteristics were suggested on inspection of the spectral data and MO calculation, and it was clarified that the positive charge is largely localized at the C11. The pK(R+) value of cation 10(+) was determined spectrophotometrically to be 4.6, which is much smaller by 4.1 pH unit than that of 1,3-dimethyl-7,12-methanocycloundeca[4,5]furo[2,3-d]pyrimidin-2,4(1,3H)-dionylium tetrafluoroborate (pK(R+) = 8.7). This value is also smaller by 1.6 pH unit than that of the parent 1,6-methano[11]annulenylium ion (pK(R+) = 6.2). The feature is rationalized on the basis of the perturbation derived from the bond fixation of the parent cation. The electrochemical reduction of 10(+) exhibited less negative reduction potential at -0.39 (V vs Ag/AgNO(3)) upon cyclic voltammetry (CV). In a search for reactivity, reactions of 10(+) with some nucleophiles, hydride and diethylamine, were carried out to give mixtures of C11- and C13-adducts. In both reactions, the methano-bridge controls the nucleophilic attacks to the C13 to favor exo selectivity. The photoinduced autorecycling oxidation reactions of 10(+).BF(4)(-) toward some amines under aerobic conditions were carried out to give the corresponding imines (isolated by converting to the corresponding 2,4-dinitrophenylhydrazones) in 719-3286% yield (recycling number of 10(+).BF(4)(-): 7.2-32.9).     

Synthesis, properties, and NAD+-NADH-type redox ability of 14-substituted 1,3-dimethyl-5,10-methanocycloundeca[4,5]pyrrolo[2,3-d]pyrimidine-2,4(1,3h)-dionylium tetrafluoroborates and their hydride adducts

A synthesis of 14-substituted 1,3-dimethyl-5,10-methanocycloundeca[4,5]pyrrolo[2,3-d]pyrimidine-2,4(1,3H)-dionylium tetrafluoroborates 11a,b(+).BF4- was accomplished by the methylation of 5,10-methanocycloundeca[4,5]pyrrolo[2,3-d]pyrimidine-2,4(1,3H)-dione derivatives with MeI and following anion-exchange reaction by treatment with 42% aq HBF(4). Compound 11b(+).BF4- was synthesized alternatively by the reaction of 1,6-methano[11]annulenylium tetrafluoroborate with 6-phenylamino-1,3-dimethyluracil and following oxidative cyclization reaction. Remarkable structural characteristics of 11a,b(+)were clarified on inspection of the UV-vis and NMR spectral data as well as X-ray crystal analyses. The stability of cations 11a,b(+)() is expressed by the pK(R+) values which were determined spectrophotometrically as 9.8 and 9.7, which are smaller by 1.4 and 1.2 pH units than those of the corresponding seven-membered ring cations, respectively; however, the values are larger by 3.6 and 3.5 pH units than that of the parent 1,6-methano[11]annulenylium ion (pK(R+) = 6.2). The feature is rationalized on the basis of the perturbation derived from the bond fixation of the parent cation and the electron-donating ability of pyrrolopyrimidine. The electrochemical reduction of 11a,b(+).BF4- exhibited reduction potential at -0.58 and -0.52 (V vs Ag/AgNO3) upon cyclic voltammetry (CV). Reaction of 11a(+).BF4- with hydride afforded mixures of the C13- and C11-adducts in a ratio with hydride afforded, on the other hand, the C13-adduct as a single product. In both cations, the methano-bridge seemed to control the nucleophilic attack to the C13 favorably with exo-selectivity. The photoinduced autorecycling oxidation reactions of 11a,b(+).BF4- toward some amines under aerobic conditions were carried out to give the corresponding imines (isolated by converting to the corresponding 2,4-dinitrophenylhydrazones) with the recycling number of 1.1 to 32.2. Furthermore, as an example of the NAD+-NADH models, the reduction of a pyruvate analogue and some carbonyl compounds with the hydride adducts of 11a,b+.BF4- was accomplished for the first time to give the corresponding alcohol derivatives.     

Novel synthesis, properties, and NAD+-NADH type redox ability of 1,3-dimethylcyclohepta[4,5]pyrrolo[2,3-d]pyrimidine- 2,4(1,3h)-dionylium ions annulated with additional pyrrolo[2,3-d]pyrimidine-1,3(2,4h)-dione and furan analogue, and their hydride adducts

[reaction: see text] A convenient preparation of novel cations 11a,b+ x BF4(-) and 12a,b+ x BF4(-), which are derived from annulation of the 1,3-dimethylcyclohepta[4,5]pyrrolo[2,3-d]pyrimidine-2,4(1,3H)-dionylium ion with additional pyrrolo[2,3-d]pyrimidine-1,3(2,4H)-dione and a furan analogue, was accomplished by a novel oxidative cyclization of 1,7-dihydro-7-[1',3'-dimethyl-2',4'(1',3'H)-dioxo-6'-(phenylamino)-pyrimidin-5'-yl]-1,3-dimethyl-10-phenylcyclohepta[4,5]pyrrolo[2,3-d]pyrimidine-2,4(1,3H)-dione 9 and its furan-analogue by using DDQ or photoirradiation under aerobic conditions. Structural characteristics of 11a,b+ and 12a,b+ were clarified on inspection of the UV-vis and NMR spectral data as well as X-ray crystal analyses. The stability of cations 11a,b+ and 12a,b+ is expressed by the pK(R+) values that were determined spectrophotometrically to be 10.7-12.6. The electrochemical reduction of 11a,b+ x BF4(-) and 12a,b+ x BF4(-) exhibited reduction potential at -0.93 to -1.00 (V vs Ag/AgNO3). The first reduction potential of 11a+ was reversible due to steric hindrance of two phenyl groups. The photoinduced oxidation reaction of 11a,b+ x BF4(-) and 12a,b+ x BF4(-) toward some amines under aerobic conditions was carried out to give the corresponding imines (isolated by converting to the corresponding 2,4-dinitrophenylhydrazones) with the recycling numbers of 0.6-30.3. Furthermore, as an example of the NAD+-NADH models, the reduction of a pyruvate analogue and some carbonyl compounds with the hydride-adduct of 11a+ x BF4(-) was accomplished for the first time to give the corresponding alcohol derivatives.     

Novel synthesis and oxidizing ability of tropylium ions annulated with two 2,4-dimethylfuro[2,3-d]pyrimidine-1(2H),3(4H)-diones

Convenient preparation of novel tropylium ions annulated with two 2,4-dimethylfuro[2,3-d]pyrimidine-1(2H),3(4H)-diones, 12a(+).BF(4)(-) and 12b(+)().BF(4)(-), consists of a reaction of 2-methoxytropone with dimethylbarbituric acid to give 7,9-dimethyl-3-[1',3'-dimethyl-2'(1'H),4'(3'H),6'(5'H)-trioxopyrimidin-5'-ylidene]cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dione 8 and the following oxidative cyclization by using DDQ or photoirradiation under aerobic conditions. On the basis of the MO calculations, the selectivity of two types of oxidative cyclization reactions of 8 was rationalized. X-ray crystal analyses and MO calculations were carried out to clarify the structural characteristics of 12a(+). BF(4)(-) and 12b(+).BF(4)(-). The stability of cations 12a(+) and 12b(+) is expressed by the pK(R) + values which were determined spectrophotometrically as 8.8 and 8.6. The electrochemical reduction of 12a(+) and 12b(+) exhibited reduction potential at -0.63 and -0.62 (V vs Ag/AgNO(3)), respectively. Reactions of 12a(+)().BF(4)(-) and 12b(+)().BF(4)(-) with some nucleophiles, hydride and diethylamine, were carried out to clarify that the reactivity of 12a(+)().BF(4)(-) and 12b(+).BF(4)(-) was substantially dependent on the annulating position. The oxidizing ability of 12a(+).BF(4)(-) and 12b(+).BF(4)(-) toward alcohols and amines in the autorecycling process was demonstrated as well.     

Synthesis, properties, and oxidizing ability of 9,11-dimethylbenzocyclohepta[6,7-b]pyrimido[5,4-d]furan- 10(9H),12(11H)-dionylium tetrafluoroborate

Convenient preparation of novel 9,11-dimethylbenzocyclohepta[6,7-b]pyrimido[5,4-d]furan-10(9H),12(11H)-dionylium tetrafluoroborate 11*BF4- consisted of a condensation reaction of benzo[d]tropone with dimethylbarbituric acid and following oxidative cyclization reaction by using DDQ-Sc(OTf)3 or photoirradiation under aerobic conditions. Alternative synthesis of 11*BF4- was also accomplished by a condensation reaction of 2-methoxybenzo[d]tropone with dimethylbarbituric acid and a subsequent cyclization reaction by using 42% aq HBF4. The X-ray crystal analysis and MO calculation were carried out to clarify the structural characteristics. Properties of the cation 11 were studied by the pKR+ value (4.7) and reduction potentials (-0.46 and -1.07 V vs Ag/AgNO3) as well as the reaction with some nucleophiles. The oxidizing ability of 11*BF4- toward alcohols in the autorecycling process was demonstrated as well.     

Synthesis of substituted pyrrolo[2,3-D]pyrimidine-2,4-diones

A facile route for the synthesis of substituted pyrrolo[2,3-d]pyrimidine-2,4-diones from substituted 2-amino-3-cyano-4-methylpyrroles is reported.     

Synthesis of Pyrano[2,3-d]pyrimidine-2,4-diones and Pyridino[2,3-d]pyrimidine-2,4,6,8-tetraones: Evaluation Antitumor Activity

A series of some novel pyrano[2,3-d]pyrimidine 4 – 10 with 75–95% yields and pyridino[2,3-d]pyrimidine derivatives 11 – 16 with 75–92% yields is reported. The building structures have been achieved by reaction of 5-arylidene barbituric acid 2 and active nucleophile carbon or nitrogen as examples barbituric acid and acetyl acetone or refluxing of bispyrimidine-2,4,6-trione derivative 3 with cyclizing reagents such as phosphorous pentoxide, hydrazine hydrate and aminothiazole. The newly synthesized structures have been elucidated on the basis of their spectral analysis. Some selected members were screened for antitumor activity. Among the screened compounds 9 , 16 , 7 , 10 and 8 exhibited high antitumor activity.     

Pyrimidines,Part XXXI . Synthesis,reactions and properties of 6-acyl-1,3-dimethylpyrrolo[2,3-d]pyrimidine-2,4-diones

Acylations of 1,3-dimethyl- ( 1 ) and 1,3,7-trimethylpyrrolo[2,3-d]pyrimidine-2,4-dione ( 2 ) with anhydrides in the presence of trifluoroacetic acid proceed well to give in good yields the corresponding 7-acyl derivatives 3–11 . The 6-trichloroacetyl derivatives 5 and 6 are sensitive towards nucleophiles, which displace the trichloromethyl group easily by formation of the corresponding 6-carboxylic acid derivatives 12–23. The newly synthesized compounds have been characterized by elemental analysis, uv and ¹H nmr spectra and pK_a, determinations.     

Synthesis of pyrrolo[2,3-d]pyrimidines (microreview)

Chemistry of Heterocyclic Compounds - Microreview summarizes recent methods for the synthesis of pyrrolo[2,3-d]pyrimidines, published since 2015. The methods are classified as Cu-catalyzed...     

Novel photo-induced oxidative cyclization of 1,3-dimethyl-5-(1-arylmethylidene)pyrimidine-2,4,6(1,3,5H)-triones: synthesis and properties of areno[5,6]pyrano[2,3-d]pyrimidine-2,4(1,3H)-dionylium ions and their photo-induced autorecycling oxidizing reaction toward some amines

Novel photo-induced oxidative cyclization was accomplished to synthesize areno[b]pyrimido[5,4-e]pyran-2,4(1,3H)-dionylium ions 13a-c⁺·ClO₄⁻. Furthermore, 13a-c⁺·BF₄⁻ and their phenyl-substituted derivatives 19a,b⁺·BF₄⁻ were alternatively synthesized by the reaction of salicylaldehyde and its naphthyl derivatives with barbituric acids and subsequent treatment with aq. HBF₄. Structural characteristics of 13a-c⁺ and 19a,b⁺ were clarified on inspection of the UV-vis and NMR spectral data as well as X-ray crystal analyses. The electrochemical properties were studied by the CV measurement. In a search for reactivity, reactions of 13a-c⁺·BF₄⁻ with some nucleophiles, hydride, benzylamine, and H₂O, were also carried out. The photo-induced autorecycling oxidation reactions of 13a-c⁺·BF₄⁻ toward some amines under aerobic conditions were carried out to give the corresponding imines (isolated by converting to the corresponding 2,4-dinitrophenylhydrazones) in 643-3600% yield (recycling number of 13a-c⁺·BF₄⁻: 6.4-36.0).     

Pyrimidines. 65. Synthesis of 6-substituted thieno[2,3-d]pyrimidine-2,4(1H,3H)-diones

Several 6-substituted thieno[2,3-d]pyrimidine-2,4(1H,3H)-dione derivatives were synthesized. 6-Ethoxycarbonyl derivatives 3 and 7 were prepared by treatment of 6-chloro-5-formyluracil 1 and 6-chloro-5-cyanouracil 6 with ethyl 2-mercaptoacetate in the presence of a base. Electrophilic substitution reactions (Vilsmeier-Haack reaction, bromination, and nitration) of 5,6-unsubstituted thieno[2,3-d]pyrimidine 9 , prepared by condensation of 6-mercaptouracil 8 with chloroacetaldehyde, afforded the corresponding 6-formyl-, 6-bromo-, and 6-nitrothieno[2,3-d]pyrimidines 10, 15 and 16 , respectively.     

Convenient Synthesis of 3-(1-Carboxyalkyl)pyrido[2,3-d]pyrimidine-2,4-diones

A cheap and safe synthetic route to obtain 3-(1-carboxyalkyl)pyrido[2,3-d]pyrimidinediones (carboxyalkyl = -CHRCO₂H; R = H; CH₂; CH₂Ph; Ph; CH₂ (C₃H₃N₂); (CH₂)₂CO₂H; CH₂CO₂H) starting from 2,3-pyridinedicarboxylic acid is described. A process scheme consistent with empirical observations is proposed.     

Isolation of Intermediates in the Synthesis of Thieno[2,3-d]pyrimidine-2,4(1H,3H)-diones Using Microwave Irradiation

A simple and fast method for the isolation of intermediates in the synthesis of 3-arylthieno[2,3-d]pyrimidine-2,4(1H,3H)-diones has been developed by microwave-assisted condensation of ethyl 2-amino-4,5-dimethylthiophene-3-carboxylate with aryl isocyanates. The intermediates, subsequently, underwent cyclization in t-butanol in the presence of potassium t-butoxide on heating to reflux to give the desired bicyclic products, 3-arylthieno[2,3-d]pyrimidine-2,4(1H,3H)-diones.     

Synthesis and properties of 1-Benzothiopyrano[2,3-d]-pyrimidine-2,4-(3H)diones (10-thia-5-deazaflavins)

Treatment of 6-arylthiouracils with the Vilsmeier reagent (dimethylformamide-phosphorus oxychloride) gave the corresponding 6-arylthio-5-formyluracils, which could alternatively be prepared by the condensation of 6-chloro-5-formyluracils with thiophenols. Dehydrative cyclization of the above 5-formyluracils with polyphosphoric acid gave 1-benzothiopyrano[2,3-d]pyrimidine-2,4-(3H)diones (10-thia-5-deazaflavins). These 10-thia-5-deazaflavins oxidized alcohols to give the corresponding carbonyl compounds with the aid of strong base, and they were hydrogenated to 1,5-dihydro-10-thia-5-deazaflavins. Treatment of 10-thia-5-deazaflavins with concentrated aqueous potassium hydroxide led to the exclusive formation of 1,5-dihydro-10-thia-5-deazaflavins and 1,5-dihydro-10-thia-5-deazaflavin-5-ones via intermolecular oxidation-reduction (disproportionation) between initially formed 1,5-dihydro-5-hydroxy-10-thia-5-deazaflavins and unchanged 10-thia-5-deazaflavins.     

A facile one-pot synthesis of new thieno- [2,3-d]pyrimidine-2,4（1H,3H）-dione derivatives

A facile one-pot synthesis of new 3-arylthieno[2,3-d]pyrimidine-2,4(1H,3H)-diones via base-catalyzed cyclocondensation of ethyl 2-amino-4,5-dimethylthiophene-3-carboxylate with aryi isocyanates is described.     

Novel synthesis, properties, and oxidizing ability of 11,13-disubstituted 3,8-methanocycloundeca[8,9-b]pyrimido[5,4-d]-furan-12(11H),14(13H)-dionylium tetrafluoroborates

Synthesis of novel 4,9-methanoundecafulvene [5-(4,9-methanocycloundeca-2',4',6',8',10'-pentaenylidene)pyrimidine-2(1H),4(3H),6(5H)-trione] derivatives 10a-c was accomplished. Their structural characteristics were investigated on the basis of the 1H and 13C NMR and UV-vis spectra. Upon treatment with DDQ, 10a-c underwent oxidative cyclization to give novel 11,13-disubstituted 3,8-methanocycloundeca[8,9-b]pyrimido[5,4-d]furan-12(11H),14(13H)-dionylium tetrafluoroborates 11a-c*BF4- in good yields. The spectroscopic properties of 11a-c*BF4- were studied, and the structural characterization of 11b*BF4- was performed by the X-ray crystal analysis. Cations 11a-c were very stable, and their pKR+ values were determined spectrophotometrically to be 8.3-8.9. The electrochemical reduction of 11a-c exhibited low reduction potentials at -0.43 to -0.45 (V vs Ag/AgNO3) upon cyclic voltammetry (CV). In a search for reactivity, reactions of 11a*BF4- with some nucleophiles, hydride and diethylamine, were carried out to clarify that the methano-bridge controls the nucleophilic attacks to occur with endo-selectivity. The photoinduced oxidation reactions of 11a*BF4- toward some amines under aerobic conditions were carried out to give the corresponding carbonyl compounds in more than 100% yield.     

Pyrimidines. LII Synthesis of pyrido[2,3-d]pyrimidine-2,4-diones and pyrido[2,3-d:6,5-d']dipyrimidine-2,4,6,8-tetrones

Reactivities of 5-dimethylaminomethylene-6-imino-1,3-dimethyluracil hydrochloride ( 1 ) toward a variety of active methylene compounds 2 and 5 were investigated. Treatment of 1 with active methylene compounds such as malononitrile and ethyl cyanoacetate in the presence of triethylamine gave pyrido[2,3-d]pyrimidine-2,4-dione derivatives 3. Reaction of 1 with barbituric acids resulted in the formation of pyrido[2,3-d:6,5-d′]di-pyrimidine-2,4,6,8-tetrone derivatives 6.     

Uncatalyzed synthesis of new substituted dihydro-2H-dipyrimido[1,2-a,4,5-d]pyrimidine-2,4(3H)-dione

Research on Chemical Intermediates - A convenient and new method has been developed for the synthesis of highly substituted dihydro-2H-dipyrimido[1,2-a,4,5-d]pyrimidine-2,4(3H)-dione derivatives by...