α-ω-Bifunctional oligomers from copolymers of conjugated dienes with isobutene

The selective oxidative cleavage of unsaturated copolymers of isobutene with conjugated diene using ruthenium tetroxide has been carried out, giving various bifunctional oligomers. A comparison between molecular weight determination and microanalysis seems to show that the nearly perfect bifunctionality obtained for the cleavage of 2,3-dimethylbutadiene-isobutene copolymer is due to the almost enclusive 1–4 configuration of the diene unit in the copolymer; some non-1–4 incorporation is apparent in the case of 1,3-pentadiene.     

Elastomers from the copolymerization of conjugated dienes and styrenes containing chlorine

Copolymers of 1,3-butadiene and o- and p-chlorostyrenes have been made by use of alkyllithium initiators. These copolymers have a uniform distribution of the chlorostyrene along the chain, suggesting that the reactivity ratio of 1,3-butadiene and chlorostyrene is close to unity.     

Sensitized photo-oxygenation of acyclic conjugated dienes

Sensitized photo-oxygenation of a wide variety of acyclic 1,3-dienes was investigated. The 1,4-cycloaddition of singlet oxygen to acyclic conjugated dienes was closely related to the thermal Diels-Alder reaction in stereospecificity, and steric and electronic effects of substituents. Reactivity order of singlet oxygen toward conjugated dienes and isolated C—C double bonds was exhibited as follows: trisubstituted mono-olefins > 2-substituted 1,3-dienes > disubstituted mono-olefins.     

Reaction of conjugated dienes with trimethyldeuterosilane

Conclusions A study was made of the reaction of butadiene, isoprene, and 3-methyl-1,4,6-heptatriene with trimethyldeuterosilane, and the location of the deuterium atom in the alkenylsilane molecule was established on the basis of the¹H and¹³C NMR spectral data, and also the mass-spectral data for dissociative electron capture. A scheme was proposed for the hydrosilylation process.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 204–208, January, 1977.     

Solvent-ligated manganese(II) complexes for the homopolymerization of isobutene and the copolymerization of isobutene and isoprene

Polyisobutenes with a high content of terminal olefinic groups can be synthesized by using manganese(II) initiators in homogeneous solution. These easily accessible complexes initiate the polymerization at room temperature and above, and afford highly reactive, gel-free polyisobutenes with high viscosities. Furthermore, the initiators were successfully used for the copolymerization of isobutene with isoprene. The high activities of the Mn(II) initiators seem to be related to their weakly coordinating nitrile ligands, which are easily displaced by substrate molecules. Replacing the nitrile ligands by other more strongly coordinating ligands such as water reduces the initiator activity significantly. The Mn(II) initiators are surprisingly resistant to temperature.     

Enantioselective and stereodivergent hydromonofluoroalkylation of conjugated and remote dienes

Because of the widespread applications of optically active alkyl fluorides in medicinal and agro chemicals, enantioselective and even stereodivergent construction of alkyl fluorides remains highly desirable but underdeveloped. Transition-metal-catalyzed asymmetric hydrofluoroalkylation of readily available dienes represents a novel route to achieve this goal, yet receives scarce study. Here we report an intriguing palladium-catalyzed enantioselective hydromonofluoroalkylation reaction of conjugated dienes. Both monosubstituted and internal dienes proceed well with the transformation and furnish alkyl fluorides in generally >80% yield and >90% ee. A stereodivergent hydromonofluoroalkylation protocol via Pd/Cu co-catalysis is also established for the access to all four stereoisomers of corresponding moieties bearing a fully-substituted F-stereogenic center and vicinal tertiary carbon center. In addition, asymmetric migratory hydromonofluoroalkylation of skipped dienes is developed to realize the direct allylic CH fluoroalkylation. A compound library of enantioenriched cyclic fluorides is thus built to highlight the transformation potential of present methodology.     

A new mechanism for the transition metal catalyzed copolymerization of conjugated dienes with olefins: The double coordination mechanism

We have focused our interest on the ethylene- butadiene copolymerizations catalyzed with Ziegler-Natta type catalysts. The catalysts used are MgCl₂ supported titanium catalysts. The main features of these copolymerizations (stereospecificity of the butadiene enchainments, multiblock structure, gel formation) cannot be rationalized on the basis of the Cossee mechanism. We propose a new model: The double coordination mechanism. It explains all the phenomena observed. Experimental confirmations will be presented in this paper.     

土木香内酯和异土木香内酯与共轭二烯的Diels-Alder反应

本文以土木香根中分离得到的土木香内酯(1)和异土木香内酯(2)为原料, 分别与环戊二烯(3)、螺[2.4]-4,6-庚二烯(4)、呋喃、蒽或丙烯醛进行Diels-Alder反应, 发现和2只与3或4发生反应, 未能得到1和2与呋喃、蒽或丙烯醛的反应产物。X射线单晶衍射法确定1或2与3的反应产物的构型, 应用高分辨核磁共振谱NOE方法确定1或2与4的反应产物的构型。     

On the valence excited states of conjugated dienes

Electron impact spectroscopic results are reported for the lowest-energy A_g and B_u valence excited states of several conjugated dienes. In all cases, the B_u state was found to lie below the A_g state. The B_u state of the s-cis compounds was found to be ≈ 0.5 eV lower in energy than that of the s-trans compounds. Correlations of these results with those obtained for several s-trans and s-cis polyenes leads to a new possible interpretation of the state observed below the B_u state in intermediate length polynes.     

共轭二烯在硅胶表面上的光氧化反应

本文选用了trans, trans-1,4-二苯基-1,3-丁二烯(DPB)分别与单重量态氧(^1O2)敏化剂亚甲基蓝(MB)或贫电子敏化剂9,10-二氰基蒽(DCA)共同吸附在硅胶表面上, 通过其光敏氧化反应来比较DPB吸附在硅胶表面与DPB在溶液中反应的异同.     

Cationic copolymerization of phenyl propenyl ethers

Ring-substituted phenyl propenyl ethers were found to form homopolymers without any rearrangement by metal halides. Phenyl propenyl ethers were less reactive than the corresponding phenyl vinyl ethers in cationic polymerization. In order to study the electronic effect of a substituent on the reactivity, cis-p-Cl,p-CH₃, and p-CH₃O-phenyl propenyl ethers were copolymerized with phenyl propenyl ether in methylene chloride at ?78°C with stannic chloride–trichloroacetic acid, and their ¹H- and ¹³C-NMR spectra were measured. The reaction constant ρ against Hammett σ_p was ?2.1. The cis-phenyl propenyl ethers were slightly more reactive than the corresponding trans isomers. On the other hand, an o-methyl group decreased the reactivity of phenyl propenyl ether. The low reactivity of o-methyl phenyl propenyl ether was attributed to the steric hindrance between the propagating carbocation and the monomer.