The photomediated reaction of alkynes with cycloalkanes
作者:Roísín A. Doohan、John J. Hannan、Niall W. A. Geraghty
DOI:10.1039/b517631j
日期:——
of a photomediator such as benzophenone, alkynes with electron-withdrawing groups react with cycloalkanes to give vinyl cycloalkanes. The reaction involves the regiospecific addition of a photochemically generated cycloalkyl radical to the beta-carbon of the alkyne. The stereochemical outcome of the reaction depends on the nature of the photomediator and alkyne used.
helical-sense polymers PR1 or PS1 were simulated using the MMFF94 program. The dependence of the NMR spectral lineshapes, optical rotations, and calculated structures on the monomer feed clearly indicated that the copolymers alternatively incorporate R1 and S1 to generate one-handed helical-sense chains. Based on these results, a polymerization mechanism is proposed, explaining a strictly alternating copolymerization
外消旋混合物和丙酸2-甲基-1-丁酯的两个手性单体,即rac 1,R 1和S 1,在甲醇中,在40° C下与催化剂[Rh(降冰片二烯)Cl] 2进行立体有规聚合。C到获得相应的螺旋形的外消旋和两个手性聚合物,P外消旋1,P - [R 1,和P小号1,和共聚物,P CO。外消旋和手性聚合物的1 H和13 C NMR谱有所不同,尽管它们的单体的NMR谱相同。的结构P共同使用一维和二维NMR,旋光度,圆二色性(CD),UV-VIS,和计算方法,以与聚合机构一起阐明的手性单体的立体化学效应与不同的手性单体比率的共聚物进行分析。线形和强度的1 H和13 C NMR光谱的温度依赖性表明,螺旋主链通过称为手风琴状螺旋振荡的三位跃迁交换绕着酯亚甲基键-O-CH 2进行受限的旋转(HELIOS)。螺旋义聚合物的能量优选结构P - [R 1或P小号1使用MMFF94程序进行了仿真。NMR谱线形状,旋光度和计算