A novel synthesis of 2,5-diphenylpyrazine

The compound C₁₆H₁₂N₂ (2,5-diphenylpyrazine) was obtained as the by-product of synthesizing 5H-Imidazol[2,3-b]isoquinoline-1-ethanol-5-one,1,2,3,10b-tetrahydro-, β(S)-phenyl-3(S)-phenyl-(compound 2), and its structure was determined by X-ray diffraction. The crystal is monoclinic, P2(1)/c, a = 13.466(5) Å, α = 90.00º, b = 5.758(2) Å, β = 93.049(9)º, c = 7.713(3) Å, γ = 90.00º, V = 597.2(4) Å³, Z = 2, Dcalc. = 1.292 mg/m³; the final R factor is R₁ = 0.0592, 771 for reflections with I ₀ > 2σ(I ₀).     

Catalytic hydroformamination of 2,5-dimethoxy-2,5-dihydrofurans

N-Substituted 3- and 4-formylpyrroles have been obtained by hydroformamination of 2,5-dimethoxy-2,5-dihydrofurans in the presence of HRh(CO)(PPh₃)₃.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1837–1840, August, 1990.     

Polymerization behaviour of 2,5-dimethylene- 2,5-dihydrofuran

Spontaneous homopolymerization of 2,5-dimethylene-2,5-dihydrofuran (DDF) was studied. The polymerization rates in two different initial monomer concentrations of DDF were analyzed with the first-order and second-order kinetics, and the homopolymerization of DDF was found to obey the first-order kinetics. The Arrhenius plot of the apparent rate constants at 30, 40, 50, and 60° gave an overall activation energy of 68.0 kJ/mol for the polymerization of DDF. From the comparison of the apparent rate constants at –78° and the time (the so-called half-life time) to decrease in half the monomer concentration for DDF with the corresponding values for p-xylylene (QM), DDF was found to be a less reactive monomer than QM. The copolymerizations of DDF with vinyl monomers such as acrylonitrile (AN), α-chloroacrylonitrile (CIAN), diethyl fumarate (DEF), and fumaronitrile (FN) were carried out in chloroform at 50° in the presence of AIBN to obtain the monomer reactivity ratios r₁(DDF) = 30.0 ± 3.0 and r₂ (AN) = 0 for the DDF-AN system, r₁ (DDF) = 1.55 ± 0.2 and r₂(CIAN) = 0 for the DDF-CIAN system, r₁(DDF) = 3.88 ± 0.2 and r₂(DEF) = 0 for the DDF-DEF system, and r₁(DDF) = 2.41 ± 0.1 and r₂ (FN) = 0 for the DDF-FN system, respectively. As the monomer reactivity ratios of r₂ for all systems were zero, Q and e values of DDF were calculated from the combination of two r₁ (DDF) values of any two copolymerization systems to be the 7.64 to 6.63 ×10²¹ range for Q and the –0.70 to –6.31 range for e, indicating that DDF is a highly conjugative and electron-donating monomer. © 1995 John Wiley & Sons, Inc.     

反式-2,5-二芳基四氢呋喃合成的新方法

以(±)4,10-二氧杂三环[5,2,1,0_2,6]-癸-8-烯-3-醇为原料,经过芳基化、氧化、芳基化、环化、热分解和加氢反应,得到PAF新的拮抗物反式-2,5-二芳基四氢呋喃,并合成了化合物8.     

A new and convergent synthesis for 2,5-diamino-tetrahydropyrimidones

AN1057A/B has shown potent activity against MRSA. A novel and concise route to the synthesis of its heterocycle core 2,5-diamino-5,6-dihydro-1H-pyrimidine-4-one is described. This methodology allows the synthesis of an array of analogs with different amine substitutions at the 2-position.     

A Dieckmann cyclization route to piperazine-2,5-diones

Piperazine-2,5-diones are formed by Dieckmann cyclization (NaH, THF) of substructures of the type CH(2)-N(R)C(O)CH(2)N(R')CO(2)Ph in which the terminal methylene (CH(2)) that is adjacent to nitrogen closes onto the carbonyl group of the phenyl carbamate unit at the other end of the chain. R and R' are alkyl groups, and the terminal methylene is activated by a ketone carbonyl, a nitrile, an ester, or a phosphoryl group. The starting materials are assembled by standard acylation and oxidation processes, starting from a β-(alkylamino)alcohol, an (alkylamino)acetonitrile, an (alkylamino) ester, or an (alkylamino)methyl phosphonate.     

Synthesis and Chemistry of 2,5-Dimethylene-2,5-Dihydrofuran

2,5-Dimethylene-2,5-dihydrofuran (3), generated flash pyrolitically, underwent di- and trimerization reactions to give cyclic dimer and trimer. Compound 3 was trapped with methanol, ethanol, bromine, acetic acid, thiophenol and oxygen. Results from trapping experiments suggest that the diradical form of 3 is involved.     

On the thermal decomposition of 2,5-dihypochloro-2,5-dimethylhexane

The title compound was prepared, characterized, and on thermal decomposition at 100°C in the presence of a chlorine atom trap was found to give acetone, 1,2-dichloroethane, and 4-chloro-2-methyl-2-butanol.     

Acid-mediated cycloalkylation of C-aminoazoles with 2,5-dimethylhexane-2,5-diol

Alkylation of 5-aminotetrazole with 2,5-dimethylhexane-2,5-diol in perchloric acid was found to proceed on an endocyclic nitrogen atom as well as on the amino group, giving 5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-4H-tetrazolo[1,5-a][1,3]diazepine. Under analogous conditions, 3-amino-1,2,4-triazole undergoes cycloalkylation of the neighboring N1 and N2 atoms of the heterocycle resulting in 1-amino-5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-[1,2,4]triazolo[1,2-a]pyridazinium perchlorate. The crystal structures of the products were determined by single crystal X-ray analysis.     

2,5-Dimethoxy-2,5-dihydrofurans in 1,3-dipolar cycloaddition reactions

Itis shown that 2,5-dimethoxy-2,5-dihydrofurans enter into 1,3-dipolar cycloaddition with benzonitrile N-oxides and with diphenylnitrilimines to form derivatives of 1,3-dimethoxy-6-phenyl-1,3,3a,6a-tetrahydrofuro[3,4-d]isoxazole and 1,3-dimethoxy-4,6-diphenyl-1,3,3a,-6a-tetrahydrofuro[3,4-d]pyrazole, respectively.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 150–151, February, 1971.     

Photochemical and chemical behaviour of 2,5-hydroperoxyhydroxy-2,5-dihydrofurans

From hydroxyhydroperoxides II and III a new bicyclic system, namely the 5,6-dioxabicyclo[2.1.1]hexane VII is obtained by photolysis or by protic acids. Epimer epoxides IV and XI are obtained on reaction with triethylamine.