A series of novel chiral diphosphite ligands have been synthesized from(1R,2R)-trans-1,2-cyclohexanediol,(1S,2S)-trans-1,2-cyclohexanediol, racemic trans-1,2-cyclohexanediol and chlorophosphoric acid diary ester, and were successfully employed in the Cu-catalyzed asymmetric 1,4-conjugate addition of diethylzinc to cyclohexenone with up to 99% ee. It was found that ligand 1,2-bis[(R)-1,10-binaphthyl-2,2'-diyl]phosphitecyclohexanediol 6a derived from racemic diol skeleton can show similar catalytic performance compared with ligand(1R,2R)-bis[(R)-1,1'-binaphthyl-2,2'-diyl]phosphitecyclohexanediol 6a' derived from enantiopure starting material. A significant dependence of stereoselectivity on the type of enone and the ring size of the cyclic enone was observed. Moreover, the configuration of the products was mainly determined by the configuration of the binaphthyl moieties of diphosphite ligands in the 1,4-addition of cyclic enones.
Pd/TiN nanocomposite catalysts were fabricated for one-step selective hydrogenation of phenol to cyclohexanone successfully. High conversion of phenol(99%) and selectivity of cyclohexanone(98%)were obtained at 30 8C and 0.2 MPa H_2 for 12 h in the mixed solvents of H_2O and CH_2Cl_2. The Pd nanoparticles were stable in the reaction, and no aggregation was detected after four successive runs.The catalytic activity and selectivity depended on slightly the Pd particle sizes. The generality of the catalysts for this reaction was demonstrated by the selective hydrogenation of phenol derivatives, which showed that the catalyst was selective for the formation of cyclohexanone.
Hai-Feng LiQin-Sheng ZhangZeng-Bo PangMi TianPing GaoLai-Lai Wang
木质素是仅次于纤维素的第二大可再生生物质资源,也是一种环境友好的有机高分子材料.原子转移自由基聚合(atom transfer radical polymerization,ATRP)是近年来迅速发展并有着重要应用价值的一种"活性"/可控自由基聚合技术.本文结合本课题组目前的研究工作和近几年的相关报道,简述了ATRP在木质素接枝共聚方面的最新研究进展.综述了采用ATRP对木质素接枝共聚改性的方法,并采用该方法在木质素表面接枝不同功能性单体,赋予木质素表面温敏性、离子响应性、气体开关和基因传递等多种特殊性能的研究概况.最后介绍了AGET ATRP(activators generated by electron transfer ATRP)在木质素接枝共聚反应中的应用.
