A Simple and Efficient Copper(Ⅱ) Complex as a Catalyst for N-Arylation of Imidazoles

Four inexpensive and air‐/moisture‐stable pyrrolecarbaldiminato‐Cu complexes 1 – 4 were synthesized and evaluated to be a novel class of catalysts for the N‐arylation of imidazoles with aryl halides. A variety of aryl iodides, bromides and activated aryl chlorides underwent the coupling with imidazoles, promoted by the catalyst 4 , in moderate to good yields without the protection by an inert gas.     

Novel Copolymers of 4-Fluorostyrene. 7. Halogen Ring-Disubstituted 2-Phenyl-1,1-dicyanoethylenes

Novel copolymers of trisubstituted ethylene monomers, halogen ring-disubstituted 2-phenyl-1,1-dicyanoethylenes, RC₆H₃CH= C(CN)₂ (where R is 2,3-Cl₂, 2,4-Cl₂, 2,6-Cl₂, 3,4-Cl₂, 3,5-Cl₂, 2-Cl-4-F, 2-Cl-6-F, 3-Cl-4-F) and 4-fluorostyrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H and ¹³C-NMR. The order of relative reactivity (1/r ₁) for the monomers is 2-Cl-4-F (2.42) > 3,4-Cl₂(2.40) > 2,4-Cl₂(1.97) > 2-Cl-6-F (1.86) > 3-Cl-4-F (1.68) > 2,3-Cl₂ (0.89) > 3,5-Cl₂ (0.70) > 2,6-Cl₂ (0.47). High T_g of the copolymers, in comparison with that of poly(4-fluorostyrene) indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Softening of the copolymers started in 194–216°C range. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 290–400°C range with residue, which then decomposed in 400–800°C range.     

Novel Copolymers of Difluoro Ring-substituted 2-Phenyl-1,1-dicyanoethylenes with 4-Fluorostyrene: Synthesis,Structure and Dielectric Study

Copolymerization of fluorine ring-substituted 2-phenyl-1,1-dicyanoethenes, RC₆H₃CH?C(CN)₂ (R is 2,3-F,F, 2,4-F,F, 2,5-F,F, 2,6-F,F, and 4-CF₃) with 4-fluorostyrene were prepared in the presence of a radical initiator (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the copolymers were characterized by IR, ¹H and ¹³C-NMR, GPC, DSC, and TGA. The monomer reactivity ratios for 4-fluorostyrene (M₁), r₁ = 0.6 and 2-(2,4-difluorophenyl)-1,1-dicyanoethene (M₂), r₂ = 0 were determined from Fineman-Ross plot. The order of relative reactivity (1/r₁) for difluoro-substituted monomers is 2,4-F,F (0.31) > 2,3-F,F (0.25) > 2,5-F,F (0.22) > 2,6-F,F (0.10). DSC curves showed that the copolymers were amorphous with high T _g in comparison with that poly(4-fluorostyrene) indicating a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer units. From the thermogravimetric analysis, the copolymers began to degrade in the range 214–260°C. The copolymer of 4-fluorostyrene and 2-(2,4-difluorophenyl)-1,1-dicyanoethene and poly(4-fluorostyrene) were dielectrically characterized in the range 25–200°C. The dominating relaxation process detected in both materials was the α-relaxation, associated with the dynamic glass transition. The relationship polarity-permittivity was discussed.     

Novel Copolymers of Styrene. 3. Some Ring-Substituted Butyl 2-Cyano-3-Phenyl-2-Propenoates

Novel trisubstituted ethylenes, ring-substituted butyl 2-cyano-3-phenyl-2-propenoates, RPhCH=C(CN)CO₂C₄H₉ (where R is 2-C₆H₅CH₂O, 3-C₆H₅CH₂O, 4-C₆H₅CH₂O, 4-CH₃COO, 3-CH₃CO, 4-CH₃CO, 4-CH₃CONH, 2-CN, 3-CN, 4-CN, 4-(CH₃)₂N, 4-(C₂H₅)₂N) were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and butyl cyanoacetate, and characterized by CHN analysis, IR, ¹H and ¹³C-NMR. All the ethylenes were copolymerized with styrene (M₁) in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, ¹H and ¹³C-NMR. The order of relative reactivity (1/r₁) for the monomers is 4-C₆H₅CH₂O (6.39) > 2-C₆H₅CH₂O (2.06) > 3-CH₃CO (1.86) > 3-C₆H₅CH₂O (1.78) > 4-CH₃COO (1.58) > 3-CN (1.47) > 4-CN (1.21) > 4-(C₂H₅)₂N (1.19) > 4-(CH₃)₂N (1.18) > 2-CN (1.04) > 4-CH₃CO (0.71) > 4-CH₃CONH (0.63). Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500°C range with residue (3.6–9.5% wt), which then decomposed in the 500–800°C range.     

Novel Copolymers of Styrene and Some Ring-substituted 2-Phenyl-1,1-dicyanoethylenes

Novel copolymers of trisubstituted ethylene monomers, ring-substituted 2-phenyl-1,1-dicyanoethylenes, RC₆H₄CH = C(CN)2 (where R is 2-F, 2-CN, 3-CN, 4-CN, 3-C₆H₅O, 4-C₆H₅O, 2-C₆H₅CH₂O, 3-C₆H₅CH₂O, 4-C₆H₅CH₂O, 4-CH₃CO₂, 4-CH₃CONH, 4-(CH₃)₂N) and styrene were prepared by solution copolymerization in the presence of a radical initiator (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H and ¹³C-NMR. The order of relative reactivity (1/r ₁) for the monomers is 4-(CH₃)₂N (3.35) > 4-C₆H₅CH₂O (3.1) > 2-C₆H₅CH₂O (1.77) > 3-C₆H₅CH₂O (1.72) > 4-C₆H₅O (1.70) > 4-CH₃CO₂ (1.58) > 2-F (1.11) > 3-C₆H₅O (0.90) > 3-CN (0.88) > 2-CN (0.86) > 4-CH₃CONH (0.84) > 4-CN (0.76). Relatively high T_g of the copolymers in comparison with that of polystyrene indicates a decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500°C range with residue (1–10% wt), which then decomposed in the 500–800°C range.     

NOVEL COPOLYMERS OF TRISUBSTITUTED ETHYLENES WITH STYRENE. I. 2-HALOPHENYL-1,1-DICYANOETHYLENES

Electrophilic trisubstituted ethylene monomers, 2-halophenyl-1,1-dicyanoethylenes, RC₆H₄CH=C(CN)₂ (where R is o-Cl, m-Cl, p-Cl, p-Br, and p-F) were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and malononitrile, and characterized by CHN elemental analysis, IR, ¹H and ¹³C-NMR. All the ethylenes were copolymerized with styrene (M₁) in solution with radical initiation (AIBN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, ¹H and ¹³C-NMR. The order of relative reactivity (1/r ₁) for the monomers is p-Cl (14.8) >m-Cl (2.67)> o-Cl (1.82) > p-Br (1.52) > p-F (1.36). High T _g's of the copolymers (> 150°C) in comparison with that of polystyrene indicate a substantial decrease in the chain mobility of the copolymers due to the high dipolar character of the trisubstituted monomer unit. Gravimetric analysis indicated that the copolymers decompose in the range 300–400°C.     

Novel and efficient multifunctional periodic mesoporous organosilica supported benzotriazolium ionic liquids for reusable synthesis of 2,4,5-trisubstituted imidazoles

A series of periodic mesoporous organosilica supported benzotriazolium ionic liquids were synthesized and tested as effective and practical heterogeneous catalysts in the condensation reaction of diphenylethanedione, aromatic aldehydes and ammonium acetate. The catalyst PMO@ILBF4(1.0) showed brilliant catalytic activity for the synthesis of 2,4,5-trisubstituted imidazoles with good to high yields. We also found that the catalytic activity could be significantly influenced by the loading levels and functional anions of the benzotriazolium-cation ionic liquid, probably due to an intensification of intramolecular synergistic effect. Furthermore, the multifunctional catalyst PMO@ILBF4(1.0) could be easily recovered by filtration and recycled for six times with no significant loss in activity, indicating its excellent stability and reusability. This method provides an efficient and environmentally-friendly procedure for the production of 2,4,5-trisubstituted imidazoles.     

Synthesis of trisubstituted thiophenesvia a halogen dance reaction at 2-bromo-5-methylthiophene

Summary A new example of a selective halogen dance reaction was observed upon lithiation of 2-bromo-5-methylthiophene withLDA under appropriate reaction conditions. A series of 2-substituted 3-bromo-5-methylthiophenes was prepared by reacting the thus selectively generated intermediate 3-bromo-2-lithio-5-methylthiophene with various electrophiles to study scope and limitations of the reaction.Dedicated to Prof. emeritusHans Suschitzky, University of Salford, UK, on the occasion of his 80^th birthday     

The One‐Pot Synthesis of 2,4,5‐Triaryl‐Imidazoles Using Heteropolyacids as Heterogeneous and Recyclable Catalysts

2,4,5‐triaryl imidazoles were obtained in high yields with excellent purity from the condensation of benzaldehydes, NH₄OAc and 1,2‐diketone in the presence of a catalytic amount of various heteropolyacids (HPAs).