Asymmetric Synthesis of Fluorinated Isoindolinones through Palladium‐Catalyzed Carbonylative Amination of Enantioenriched Benzylic Carbamates

The asymmetric synthesis of fluorinated isoindolinones has been achieved by a palladium‐catalyzed aminocarbonylation reaction of the corresponding α‐fluoroalkyl o‐iodobenzylamines. A base‐mediated anti β‐hydride elimination process was suggested to explain the partial erosion of the optical purity observed in some cases. This mechanistic rationale enabled the minimization of this partial racemization by fine‐tuning the pK_a of the base.     

A Convenient Palladium‐Catalyzed Carbonylative Suzuki Coupling of Aryl Halides with Formic Acid as the Carbon Monoxide Source

A practical palladium‐catalyzed carbonylative Suzuki coupling of aryl halides under carbon monoxide gas‐free conditions has been developed. Here, formic acid was utilized as the carbon monoxide source for the first time with acetic anhydride as the additive. A variety of diarylketones were produced in moderate to excellent yields from the corresponding aryl halides and arylboronic acids.     

Ni-Sn-Cr/AC催化剂上乙酸甲酯气相羰基化合成醋酐反应的研究

以活性炭为载体,采用浸渍法制备Ni-Sn-Cr/AC催化剂,在连续流动固定床反应器上研究其对乙酸甲酯气相羰基化合成醋酐反应的催化性能。分别考察了Ni、Sn、Cr三种金属组分的负载量对催化活性的影响,进一步考察了反应压力、反应温度、反应时间对反应的影响。实验结果表明,在Ni9%-Sn12%-Cr6%/AC催化剂上,当反应温度205℃,压力5.5MPa,催化剂焙烧温度600℃,催化剂焙烧时间为4h的条件下,乙酸甲酯的转化率为38.8%,醋酐的选择性为81.1%。采用X射线衍射和元素分析技术分别对反应前和不同反应时间后的催化剂进行了表征。分析结果表明,Ni⁰是催化剂的主要活性中心,随着反应时间的延长,活性组分镍的流失现象比较严重,同时催化剂上出现积炭及载体骨架遭到破坏,是导致催化剂失活的主要原因。     

钯催化烯烃不对称羰基化反应的研究进展

钯催化烯烃不对称羰基化反应是一种合成手性羰基化合物的有效方法之一,综述了近年来钯催化烯烃不对称羰基化反应的最新研究进展,重点讨论了配体、催化体系、反应条件等因素对烯烃羰基化反应的影响,并对烯烃不对称羰基化反应的区域选择性和对映选择性以及可能的反应机理进行了探讨.     

Carbonylation of nitrobenzene in methanol with palladium bidentate phosphane complexes: an unexpectedly complex network of catalytic reactions, centred around a Pd-imido intermediate

The reactivity of palladium complexes of bidentate diaryl phosphane ligands (P₂) was studied in the reaction of nitrobenzene with CO in methanol. Careful analysis of the reaction mixtures revealed that, besides the frequently reported reduction products of nitrobenzene [methyl phenyl carbamate (MPC), N,N′‐diphenylurea (DPU), aniline, azobenzene (Azo) and azoxybenzene (Azoxy)], large quantities of oxidation products of methanol were co‐produced (dimethyl carbonate (DMC), dimethyl oxalate (DMO), methyl formate (MF), H₂O, and CO). From these observations, it is concluded that several catalytic processes operate simultaneously, and are coupled via common catalytic intermediates. Starting from a P₂Pd⁰ compound formed in situ, oxidation to a palladium imido compound P₂Pd^II?NPh, can be achieved by de‐oxygenation of nitrobenzene 1) with two molecules of CO, 2) with two molecules of CO and the acidic protons of two methanol molecules, or 3) with all four hydrogen atoms of one methanol molecule. Reduction of P₂Pd^II?NPh to P₂Pd⁰ makes the overall process catalytic, while at the same time forming Azo(xy), MPC, DPU and aniline. It is proposed that the Pd–imido species is the central key intermediate that can link together all reduction products of nitrobenzene and all oxidation products of methanol in one unified mechanistic scheme. The relative occurrence of the various catalytic processes is shown to be dependent on the characteristics of the catalysts, as imposed by the ligand structure.     

CuY制备方法对其催化甲醇氧化羰基化活性中心的影响

以Cu(NO₃)₂为铜源,以NaY和HY分子筛为载体,通过溶液离子交换法和等体积浸渍法制备了不同的无氯CuY催化剂,并进行了气相甲醇氧化羰基化催化活性研究。通过浸渍法制备的催化剂Cu含量为10%,而以NaY和铜氨溶液离子交换制备的催化剂Cu含量只有6.3%,但其催化活性和选择性均较好。通过催化剂的Cu元素分析、低温氮吸附-脱附、XRD、H₂-TPR、XPS和TPD等表征表明,溶液离子交换法制备的催化剂,Cu物种以离子的形式高度分散于分子筛骨架结构中,较好地保持了分子筛晶体结构,并对甲醇有较强的吸附能力,催化活性较高,而将等体积浸渍Cu(NO₃)₂溶液后的HY或NaY分子筛,在400 ℃焙烧过程中,发生了固体离子交换反应,形成了连接于分子筛骨架的Cu²⁺,但以HY为载体更容易进行固体离子交换,未交换的铜物种以CuO的形式分散到分子筛表面。在600 ℃高温活化中,催化剂中Cu²⁺可部分还原为活性物质Cu⁺,但以NaY和铜氨溶液离子交换制备的催化剂Cu²⁺自还原能力最大。     

Oxidative carbonylation reactions: organometallic compounds (R-M) or hydrocarbons (R-H) as nucleophiles

Oxidative carbonylation reactions have attracted broad interest from both academia and industry in recent years. Enormous efforts have gone into the syntheses of carbonate and urea derivatives through the oxidative carbonylation of alcohols and amines. Very recently, organometallic reagents (R-M) and hydrocarbons(R-H) were directly employed as nucleophiles to construct a C-C bond in oxidative carbonylation reactions. This Minireview summarizes this novel type of oxidative carbonylation reaction.     

Oxidative addition of different electrophiles with rhodium(I) carbonyl complexes of unsymmetrical phosphine–phosphine monoselenide ligands

Dimeric chlorobridge complex [Rh(CO)₂Cl]₂ reacts with two equivalents of a series of unsymmetrical phosphine–phosphine monoselenide ligands, Ph₂P(CH₂)_nP(Se)Ph₂ {n = 1( a ), 2( b ), 3( c ), 4( d )}to form chelate complex [Rh(CO)Cl(P∩Se)] ( 1a ) {P∩Se = η²‐(P,Se) coordinated} and non‐chelate complexes [Rh(CO)₂Cl(P～Se)] ( 1b–d ) {P～Se = η¹‐(P) coordinated}. The complexes 1 undergo oxidative addition reactions with different electrophiles such as CH₃I, C₂H₅I, C₆H₅CH₂Cl and I₂ to produce Rh(III) complexes of the type [Rh(COR)ClX(P∩Se)] {where R = ? C₂H₅ ( 2a ), X = I; R = ? CH₂C₆H₅ ( 3a ), X = Cl}, [Rh(CO)ClI₂(P∩Se)] ( 4a ), [Rh(CO)(COCH₃)ClI(P～Se)] ( 5b–d ), [Rh(CO)(COH₅)ClI‐(P～Se)] ( 6b–d ), [Rh(CO)(COCH₂C₆H₅)Cl₂(P～Se)] ( 7b–d ) and [Rh(CO)ClI₂(P～Se)] ( 8b–d ). The kinetic study of the oxidative addition (OA) reactions of the complexes 1 with CH₃I and C₂H₅I reveals a single stage kinetics. The rate of OA of the complexes varies with the length of the ligand backbone and follows the order 1a > 1b > 1c > 1d . The CH₃I reacts with the different complexes at a rate 10–100 times faster than the C₂H₅I. The catalytic activity of complexes 1b–d for carbonylation of methanol is evaluated and a higher turnover number (TON) is obtained compared with that of the well‐known commercial species [Rh(CO)₂I₂]^?. Copyright © 2006 John Wiley & Sons, Ltd.     

甲醇多相羰化制甲酸甲酯新催化体系的研究

甲酸甲酯（MF）是用途广泛的低沸点溶剂和基本有机合成的重要中间体，近年来又逐渐发展为动力燃料的添加剂[1]．迄今MF主要由甲醇液相羰化法生产[2]，但该法存在时空收率低，催化剂与产物需进行分离，反应不能连续进行等弊端[3]。文献[4]曾报道过一种可用于多相体系的阴离子强碱交换树脂，但其催化活性太低，尚看不出有太大的实用价值．本文开发了一种负载型强碱液膜催化剂，在固定床连续流动反应器中首次实现了甲醇多相催化羰化制甲酸甲酯，其催化活性及时空产率明显优于均相催化体系[5]．1实验部分催化剂由碱金属醇化物、液膜相溶剂（甲…