Spontaneous copolymerization of 1,3-cycloheptadiene with acrylonitrile in the presence of zinc chloride

The reaction of 1,3-cycloheptadiene (1,3-CHpD) with acrylonitrile (AN) in the presence of ZnCl₂ leads spontaneously to the simultaneous formation of an alternating copolymer and a small amount of cycloadduct. The copolymer has a predominantly cis-1,4-structure. The formation of the charge—transfer complex between 1,3-CHpD and (AN)c (AN coordinated to ZnCl₂) in AN was detected by ultraviolet (UV) spectroscopy. The activation energies for the cycloaddition and for the copolymerization under the conditions used were determined to be 17.6 (in the presence of 1,1-diphenyl-2-picrylhydrazyl) and 16.3 kcal/mole, respectively. The rate of copolymerization in AN was found to depend on the 1.5th power of the concentrations of (AN)c and of 1,3-CHpD. Oxygen and UV irradiation causes an acceleration of the copolymerization only. On the basis of these results the mechanism of the spontaneous copolymerization is discussed and its relation to the cycloaddition in systems of 1,3-cyclodienes and AN in the presence of ZnCl₂ is mentioned.     

Polymeric formamides as liquid–liquid phase transfer catalysts

Polymeric formamides were prepared by free radical polymerization of N-methyl-N-vinyl-formamide or N-methyl-N-(4-vinylbenzyl)formamide, and copolymerization of these monomers with styrene. These soluble polymers serve as phase transfer catalysts for several reactions under liquid–liquid biphase conditions. The catalytic activity of copolymers containing styrene unit is affected remarkably by composition, and there are maxima at certain composition in both polymers. However, copolymers with an acrylonitrile co-unit scarcely exhibit catalytic activity. Furthermore, it was found that these polymers can extract all alkali metal ions employed here, and that the extraction ability increases with increasing the density of active sites. From these results, it is demonstrated that catalytic activity strongly depends on both cation extraction ability of polymers and lipophilicity around the active sites in the polymer.     

Epimerization of diastereomeric alpha-amino nitriles to single stereoisomers in the solid state

[reaction: see text] A diastereomeric mixture of the alpha-amino nitrile prepared by the Strecker reaction of benzaldehyde, (1S,2R)-1-aminoindan-2-ol, and cyanotrimethylsilane thermally epimerizes in the solid state to give a single diastereomer with an (S)-configuration at the alpha position to the nitrile moiety. This shows a sharp contrast to the reaction conducted in DMSO at room temperature, which gives a 1:1 mixture of (S)- and (R)-isomers. Several other alpha-amino nitriles also epimerize in the solid-state toward single diastereomers.     

Cationic vesicles consisting of 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) and phosphatidylcholines and their interaction with erythrocyte membrane

We studied the formation and stability of vesicles consisting of 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) and phosphatidylcholines by electron spin resonance (ESR) analysis and observation of their hemolytic activities. In contrast with previous findings on dimethyldialkylammoniums, DOTAP formed vesicles at 37 degrees C with phosphatidylcholines containing either saturated acyl chains such as dimyristoylphosphatidylcholine (DMPC) or unsaturated acyl chains such as dilinoleoylphosphatidylcholine (DLPC). Phosphatidylcholines made the bilayer more rigid and significantly reduced the hemolytic activity of DOTAP. In the presence of equimolar concentration of DOTAP and phosphatidylcholines, formation of tightly aggregated structures of several erythrocytes was observed, as previously reported for the vesicles containing dimethyldipalmitylammonium. These findings indicate that DOTAP vesicles were stabilized by phosphatidylcholines with either saturated acyl chains or unsaturated acyl chains, and the interaction with the lipid bilayer of biological membranes as cationic vesicles became prominent with minimal membrane damage by DOTAP monomers.     

蝶状铁硫磷簇合物(μ-Ar_2P)(μ-RS)Fe_2(CO)_6与(μ-p-CH_3C_6H_4PCl)(μ-RS)Fe_2(CO)-6的合成及表征

本文报道通过由Fe_3(CO)_(12)/RSH/Et_3N体系所形成的中间物[(μ-CO)(μ-RS)Fe_2(CO)_6]Et_3NH与Ph_2PCl,(p-CH_3C_6H_4)_2PCl或p-CH_3C_6H_4PCl_2反应,合成了7个蝶状Fe_2SP簇合物: (μ-Ph_2P)(μ-RS)·Fe_2(CO)_6(R=Pr~(?),Pr~(?),Bu~(?))、[μ-(p-CH_3C_6H_4)_2P](μ-Pr(?)S)Fe_2(CO)_6以及(μ-p-CH_3C_6H_4PCl)(μ-RS)Fe_2·(CO)_6(R=Et,Pr~(?),Bu~(?))。并对它们的~1H NMR、~(31)P NMR波谱与构象体的关系以及簇合物(μ-Ph_2P)(μ-Bu~(?)S)Fe_2(CO)_6的催化活性进行了初步探讨。     

22,-Dimethyl-4-phenyloxazoline and 2,2-dimethyl-4,5-diphenylimidazolidine as new chiral auxiliaries. Applications to asymmetric nitrile oxide cycloadditions

Asymmetric dipolar cycloadditions of a nitrile oxide to the acrylamide derivatives of two new chiral auxiliaries, (R)-2,2-dimethyl-4-phenyloxazolidines and (S,S)-2,2-dimethyl-4,5-diphenylimidazolidine, show satisfactorily high diastereoselectivities (up to 91%).     

Origin of facial diastereoselection. Evidence for negative role of antiperiplanar hyperconjugation effects in the transition state of carbene insertion

[reaction: see text] Quantitative analysis of the transition state (TS) structures of the insertion reactions of 5-X-2-adamantanylidenes (X = H, OH, NH(2), SiMe(3)) into MeOH or cyclohexane revealed that the magnitude of antiperiplanar hyperconjugative stabilization involving the incipient bond effects (the AP effect) decrease at TS, strongly suggesting that the AP effect contributes "net destabilization" of TS (i.e., increase in activation energy), in sharp contrast to the proposals of the Felkin-Anh and the Cieplak models. The equilibrium population between two carbene bridge-flipping proximal-distal conformers was found to be the origin of facial diastereoselection of these carbenes.     

溶剂化金属原子浸渍法制备高分散负载型催化剂——Ⅱ,Fe,Co,Ni催化剂的分散度和催化性能研究

本文利用一种新的方法-溶剂化金属原子浸渍法制备了Fe/γ-Al_2O_3,Fe/SiO_2,Co/γ-Al_2O_3,Co/SiO_2,Ni/γ-Al_2O_3和Ni/SiO_2六种催化剂。H_2化学吸附,TEM和XRD测定结果表明这些催化剂中Fe,Co,Ni金属颗粒平均直径都小于30A,金属分散度均大于50%。作者研究了Fe/γ-Al_2O_3,Co/γ-Al_2O_3和Ni/γ-Al_2O_3三种催化剂在CO+H_2反应中的催化行为,测定了碳氢产物分布和比催化活性,表明随着H_2/CO比增大和反应温度升高。较高分子量物种产量减少,有利于生成甲烷。催化剂的活性大小次序为Fe>Ni>Co。