Convenient one-pot synthesis of functionalized cyclopentene via Sm/TMSCI/t-BuOH system mediated hydrodimerization cyclization of gem-diactivated alkene

Functionalized cyclopentenes could be prepared through Sm/TMSCl/t-BuOH mediated hydrodimerization cyclization of gem-diactivated alkene in one-pot at room temperature. The trans- or trans, transform isomer is in the majority and the major product was isolated from its stereoisomers through the fractional crystallization method.     

Significant rate acceleration of the aza-Michael reaction in water

The addition of amines to conjugated alkenes has been carried out in water at room temperature very efficiently without any catalyst. Significant rate acceleration of this reaction is observed in water compared to organic solvents.     

Effect of triarylphosphane ligands on the rhodium‐catalyzed hydrosilylation of alkene

A series of triarylphosphanes ( 1a , 2a , 3a , 4a , 5a , 6a , 7a , 8a , 9a , 10a , 11a ) have been synthesized. An X‐ray crystal structure analysis of (2‐bromophenyl)diphenylphosphane ( 1a ) unambiguously confirmed the constitution of the functionalized phosphane. The hydrosilylation reaction of styrene with triethoxysilane catalyzed with RhCl₃/triarylphosphane was studied. In comparison with the classic Wilkinson's catalyst, rhodium complexes with functionalized triarylphosphane ligands are characterized by a very high catalytic effectiveness for the hydrosilylation of alkene. Among these catalysts tested, RhCl₃/diphenyl(2‐(trimethylsilyl)phenyl)phosphane ( 8a ) exhibited excellent catalytic properties. Using this silicon‐containing phosphane ligand for the rhodium‐catalyzed hydrosilylation of styrene, both higher conversion of alkene and higher β‐adduct selectivity were obtained than with Wilkinson's catalyst. Copyright © 2014 John Wiley & Sons, Ltd.     

Silylenes,Silenes, and Disilenes: Novel Silicon‐Based Reagents for Organic Synthesis?

Silylenes, silenes, and disilenes are silicon analogues of carbenes and alkenes. Since the first detection and isolation of these species a few decades ago, focus has been given to their fundamental structure and reactivity properties. Recent developments show that the time is set to exploit their unique chemistry in applied areas. Emerging applications in catalysis and stereoselective synthesis point to a new field within synthetic organosilicon chemistry.     

二氧化碳加氢合成低碳烯烃反应平衡体系热力学研究

 随着世界工业的发展,含碳物质氧化的最终产物CO2的排放量与日俱增,CO2温室气体对环境的污染已引起人们广泛的关注. 研究证明,CO2可作为单体转化为烃进行二次利用,是最有前景的抑制其大量排放的途径. 在化学反应工程上,热力学研究可以为反应体系提供一个反应物转化率的理论最大值,从而更加清楚地认识这一反应体系,为衡量催化剂的效果提供有利的尺度,进而指导催化剂的开发工作. 对CO2加氢合成低碳烯烃反应体系平衡时进行了热力学研究,通过数学方法对催化作用下反应体系的热力学参数进行求解,分析了反应体系平衡时各相的平衡组成及其同温度、压力和氢/碳比之间的关系. 结果表明,CO2理论最高转化率为69%~71%.     

Highly Active Syndiospecific Living Polymerization of Higher 1‐Alkene with ansa‐Fluorenylamidodimethyltitanium Complex

1‐Hexene polymerization was conducted by [t‐BuNSiMe₂(3,6‐t‐Bu₂Flu)]TiMe₂ ( 1 ) using trialkylaluminum‐free modified methylaluminoxane (dMMAO) as a cocatalyst in toluene. The system produced living syndiotactic poly(1‐hexene) with high turnover frequency of propagation (TOF, 98 s⁻¹) at 0 °C. The propagation rate was increased linearly against the 1‐hexene concentration, which indicates that the first‐order dependence of the propagation rate on monomer concentration. Polymerizations of 1‐octene, 1‐decene and 1‐dodecene were also conducted for investigating the effect of chain length of 1‐alkene on propagation rate by means of the livingness of this system. The propagation rate decreased according to the chain length until 1‐decene but almost unchanged in longer 1‐alkene: TOF, 1‐octene (62 s⁻¹)>1‐decene (32 s⁻¹) ≈ 1‐dodecene (31 s⁻¹).

     

Tetrasubstituted bisadamantylidenes—Highly twisted alkenes

A number of 1,3,1′,3′‐tetrasubstituted bisadamantylidenes are examined with 4 different density functional methods (BP86‐D3, ωB97X‐D, B3LYP, and B3LYP‐D3) and the 6‐311G(d) basis set. With increasing steric bulk, these substituted bisadamantylidenes become ever more twisted about the central carbon‐carbon double bond. This manifests in significantly reduced singlet‐triplet gaps from that of typical alkenes, with the tetra‐t‐butylbisadamantylidene 17 , twisted to almost 90°, having a gap of only 2.2 kcal mol^?1. While its large strain energy may preclude the synthesis of 17 , other less‐strained tetrasubstituted analogues are more feasible synthetic targets and still possess small singlet‐triplet gaps, which should be testable by variable temperature NMR and EPR spectroscopy. The twisted alkenes also result in a low rotational energy barrier, and 4 examples with a low barrier to cis‐trans isomerization are presented. These too should be testable by experiment.     

Positional and Geometrical Isomerisation of Alkenes: The Pinnacle of Atom Economy

Strategies to achieve spatiotemporal regulation of pre‐existing alkenes via external stimuli are essential given the ubiquity of feedstock olefins in chemistry and their downstream applications. Mirroring the 1‐0 switch that underpins mammalian vision through selective geometric isomerisation in retinal, strategies to manipulate 2D space by both geometric and positional isomerisation of alkenes via chemical, thermal and light‐driven processes are being intensively pursued. This minireview highlights the current state of the art in activating and achieving directionality in these fundamental chemical transformations.     

氢自由基引发的1,2-炔基迁移

报道了一类新颖的Fe(III)介导的形式上的非活性烯烃的氢炔化反应. 该反应利用Fe(acac)₃与苯硅烷反应能原位产生氢自由基的特性实现了氢自由基诱导的1,4-烯炔的分子内1,2-炔基迁移, 合成了一系列α-炔酮类化合物, 产率中等到良好. 基于实验结果及文献报道, 提出了可能的反应机理, 其涉及氢自由基加成、3-exo-dig环化(反鲍德温规则)和 C—C键的断裂重组等. 此外, 该反应具有良好的官能团兼容性, 如雌酮衍生的1,4-烯炔也能成功参与该反应.     

Carbon‐Carbon and Carbon‐Heteroatom Bond Formation Reactions Using Unsaturated Carbon Compounds

The carbon‐carbon and carbon‐heteroatom bond formation reactions are considered as a fundamental tool in synthetic organic chemistry. They have been effectively utilized in the synthesis of medicinally significant molecules, agrochemicals and valuable compounds in material sciences. This has been primarily enabled by highly efficient protocols arising from divergent mechanistic pathways. In this personal account, we aim to discuss some recent advances in carbon‐carbon or carbon‐heteroatom bond formation reactions to which our group has actively contributed. More specifically, this record focuses on the use of unsaturated carbon compounds for the construction of C?C and C?X bonds.