Bulky Achiral Triarylphosphines Mimic BINAP in Ru(II)‐ Catalyzed Asymmetric Hydrogenation of Ketones

In the present work, we report on catalysis of the enantioselective hydrogenation of ketones with Ru(II) complexes composed of cheap achiral monodentate phosphine ligands in combination with an enantiopure 1,2‐diamine, affording a variety of optically active secondary alcohols with high efficiency and enantioselectivity. The steric impact of achiral monophosphine ligands in Ru complexes was found to be a critical factor for the high enantioselectivity of the reaction. This finding throws some light on a long‐standing challenge, the high cost of chiral bisphosphine ligands, associated with an industrial application of the asymmetric hydrogenation of ketones.     

Modular Furanoside Diphosphite Ligands for Pd‐Catalyzed Asymmetric Allylic Substitution Reactions: Scope and Limitations

We have synthesized a library of furanoside diphosphite ligands for the Pd‐catalyzed allylic substitution reactions of acyclic and cyclic allylic esters. The library has been designed to rapidly screen the ligands to uncover their important structural features and to determine the scope of diphosphite ligands in these catalytic reactions. After the systematic variation of the sugar backbone, the substituent at C‐5 and the phosphite moieties, the diphosphite ligand 4c was found to be optimal in the Pd‐catalyzed asymmetric allylic substitution of hindered ( S1 ) and unhindered ( S2 – S5 ) substrates, yielding high activities [TOFs up to >3000 mol×(mol×h)⁻¹] and enantioselectivities (ees up to 99%). In addition, the screening of the library enabled us to find other suitable ligands for hindered disubstituted linear substrate S1 (ligands 1b – d, g and 4b, d, g ) and for unhindered cyclic substrates S3 – S5 ( ligands 6c and 7c ).     

A New Chiral P,N‐Ligand Derived from 1‐Phenylphospholane‐2‐carboxylic Acid (Phenyl‐P‐proline) for Palladium‐Catalyzed Asymmetric Allylic Substitution Reactions

New types of P,N‐ligands, cis‐ and trans‐ 3 , containing a tetrahydroisoquinoline skeleton as an N‐donor were synthesized from (1R,2S)‐1‐phenylphospholane‐2‐carboxylic acid (phenyl‐P‐proline, 1 ). The cis isomer, cis‐ 3 , was found to act as an excellent ligand in palladium‐catalyzed asymmetric allylic substitution reactions. The reactions of 1,3‐diphenyl‐2‐propenyl acetate ( 5 ) with several nucleophiles in the presence of [Pd(π‐allyl)Cl]₂, cis‐ 3 (Pd : ligand=1 : 2), and a base afforded the desired products in high yields with high enantioselectivity. It was suggested that these ligands did not serve as P,N‐bidentate ligands but as P‐monodentate ligands in these reactions.     

Highly Air‐ and Water‐Stable Fluorinated Ferrocenylphosphine‐Aminophosphine Ligands and their Applications in Asymmetric Hydrogenations

Air‐ and water‐stable fluorinated ferrocenylphosphine‐aminophosphine ligands have been synthesized and applied to the Rh‐catalyzed asymmetric hydrogenation of enamides and α‐dehydroamino acid derivatives. These reactions afforded the corresponding products in good to excellent ees (up to 99.7% ee) and nearly quantitative yields. The combination of the remarkable air‐ and water‐stability with excellent catalytic performance makes these catalysts excellent choices for practical applications.     

Periodicity Characteristic of TOAD' s Switching Window

The periodicity characteristic of switching window of a terahertz optical asymmetric demultiplexer (TOAD) using numerical simulation was investigated. The results show that the switching window width of TOAD changes periodically with the time asymmetry of TOAD and the period is one half of the period of control pulses. The theoretical results agree with the experimental results very well.     

不对称脊波导截止波长的计算

将计算矩形波导和对称脊波导导内波长的横向谐振法推广用于计算不对称单脊波导的导内波长和电中心线对波导宽边几何中心线的偏置。介绍了为保证脊波导截止波长或导内波长不变的情况下,设计不对称脊波导的方法,并给出了一些计算结果和试验结果。     

用不对称的P/V操作设计并发算法

多线程并发是提高系统性能的常用手段,文章提出了一种用信号量的不对称P/V操作来设计多线程并发算法的新思路,这种思路适合于设计多线程同步程序以解决某些具有复杂同步语义要求的问题,而这些问题用传统的方法很难得到简洁高效的求解。为了演示这种新思路的特点和优点,笔者对几个常见问题(读写锁、排队锁和记录锁)给出了新的算法设计以及实现。实验数据表明,采用这种思路设计的算法在算法复杂度,读写速度和资源使用方面相对于传统的算法存在较大优势。     

Impacts of uncertain project duration and asymmetric risk sensitivity information in project management

This paper investigates the impacts of uncertain project duration and asymmetric risk sensitivity information on the structure of incentive contract and profits in project management where a risk‐neutral project manager (she) engages a risk‐averse contractor (he) to complete a project. The project manager offers a duration‐based incentive contract to the contractor to ensure that he invests his effort to shorten the project duration and reports his risk sensitivity information truthfully. Within the framework of principal‐agent theory, we first develop a duration‐based incentive contract model, and then derive the optimal contract mechanism by solving its equivalent optimal control problem with Pontryagin maximum principle. We show that if the contractor is highly risk averse and the project duration is highly volatile, the project manager should lower the penalty term to motivate the contractor to make duration‐reduction efforts. Moreover, comparing with the symmetric information scenario, we find that the project manager distorts the penalty term for all contractor's risk types (but the lowest) downward. Our results show that the project manager is more willing to acquire the contractor's risk sensitivity information under the uncertain project duration. The results also suggest that from the project manager's perspective, it is beneficial to have better information about the contractor's risk sensitivity by using a numerical analysis.     

非对称风幕出口阻隔效果正交实验研究

矿用空气幕作为先进的井下风流调控技术,可以有效地解决井下通风与交通的矛盾。为提高风幕阻隔风流的效率,对比了单风机风幕在风量一定的条件下,不同出口布置形式对阻隔效果的影响,发现双侧非对称形式优于其他形式,为进一步研究在该形式下各因素对风幕阻隔效果的影响,利用正交实验原理设计了影响矿用风幕阻隔效果的四因素三水平的数值实验。