多相CeO_2催化剂上氧化吲哚与醛的选择性C3烯基化反应（英文）

本文报道了将市售CeO_2作为一种高活性和可重复使用的催化剂用于无溶剂条件下氧化吲哚与醛的C3选择性烷基化反应.这种催化方法一般适用于不同的芳香族和脂肪族醛,得到3-烷基二烯-辛醇,产率高(87%–99%),立体选择性高(79%–93%为E-异构体).这是从氧化吲哚与各种脂肪族醛催化合成3-烯基氧化吲哚的首例.采用原位红外光谱研究了CeO_2上Lewis酸位点与苯甲醛之间的Lewis酸-碱相互作用.不同粒径CeO_2催化剂的构效关系研究表明,无缺陷CeO_2表面是该反应的活性中心.     

Au(I)/手性双功能叔胺催化实现的一锅法串联成烯/不对称环化反应构建螺环季碳氧化吲哚

研究报道了Au（I）/手性叔胺串联催化实现的一锅法不对称反应,实现从重氮氧化吲哚和氟代烯醇硅醚出发构建螺环季碳氧化吲哚.反应的第一步是3.0 mol% IPrAuBF₄催化的重氮氧化吲哚与单氟烯醇硅醚的交叉偶联反应,现场产生N-Ac保护的3-烯基氧化吲哚在手性叔胺-四方酸C1的催化下与N-Ts邻氨基查尔酮再发生不对称Michael/Michael反应,以中等到良好的产率以及对映选择性,>20：1的非对映选择性得到螺环季碳氧化吲哚.反应的关键一步是Au（I）催化的给体-受体类重氮化合物与三取代单氟烯醇硅醚的成烯化反应,高效构建三取代烯烃.     

吲哚-环丙烷的分子内开环反应※

本工作使用In(NTf₂)₃作为金属Lewis酸催化剂, 实现了吲哚-环丙烷分子内的亲核开环反应, 克服了脂肪族取代的环丙烷活性低、不易实现开环反应的难题. 利用该方法可以简单高效地构建吡咯并[1,2-a]-吲哚骨架结构的化合物. 该反应条件温和, 底物普适性广, 最终以15个反应实例, 高达96%收率得到一系列吡咯并[1,2-a]-吲哚化合物.     

烯丙基转移反应合成直链高烯丙基醇

研究了不同脂肪族和芳香族醛与6-甲基-6-苯基-7-烯-1,5-辛二醇的烯丙基转移反应, 同时考察了溶剂对反应的影响. 结果发现, 在In(OTf)3催化下, 以甲苯为溶剂, 由脂肪族醛合成的直链高烯丙基醇较芳香族醛具有较高的产率和较好的选择性, 所得产物结构经1H NMR, 13C NMR, IR, HRMS表征.     

乙酰丙酮氧钒催化氧化α-蒎烯一步转化成龙脑烯醛

以乙酰丙酮氧钒为催化剂,过氧化氢为氧化剂,研究了由α-蒎烯直接合成龙脑烯醛的反应。考察了溶剂、温度、催化剂用量、反应时间等因素对催化性能的影响。结果表明,乙酰丙酮氧钒与H2O2反应得到的高价态V5+是优良的氧化还原-Lewis酸双功能催化剂,易使α-蒎烯经氧化、2,3-环氧蒎烷异构得到龙脑烯醛。在n(H2O2):n(α-蒎烯):n(乙酰丙酮氧钒)=2.5:1:0.01、反应温度为20℃、丙酮为溶剂、反应2h条件下,α-蒎烯转化率为50.2%,龙脑烯醛的选择性达58.7%,反应6h后α-蒎烯转化率可达73.0%,主要产物龙脑烯醛和马鞭草烯酮的选择性分别为47.2%和13.2%。     

通过η~3-苄基钯中间体零价钯催化的吲哚苄基化反应(英文)

本文报道了零价钯催化的吲哚苄基化反应,获得了优秀的区域选择性.使用Pd(PPh3)4作为催化剂,在温和反应条件下,以90%–99%的收率获得含有各类取代吲哚片段的三芳基甲烷化合物.     

螺氮杂环丙烷氧化吲哚的不对称合成研究

螺环氧化吲哚和氮杂环丙烷都是非常重要的活性骨架,以3-烯氧化吲哚和双保护的羟胺为起始原料,基于Michael加成-取代串联反应,实现了螺氮杂环丙烷氧化吲哚的不对称合成.通过对一系列手性催化剂、反应温度等的筛选,最终确定了奎宁和辛克宁为最优催化剂,分别以28%和34%的对映选择性得到目标产物,其结构经过1~H NMR、~(13)C NMR和HRMS确定.     

金鸡纳硅醚衍生物有机催化吲哚与靛红的不对称Friedel-Crafts反应

金鸡纳硅醚衍生物用于有机催化不同吲哚和靛红的不对称Friedel-Crafts反应.筛选出最佳的催化剂体系,以78％～96％的产率和最高达99％的对映选择性获得了手性3-羟基-2-吲哚酮.拓宽了该反应的催化剂类型和底物范围.     

不对称双酸催化吲哚的Friedel-Crafts烷基化反应:抗衡阴离子调控对映选择性

研究了双酸催化剂对吲哚和β,γ-不饱和α-酮酸酯的不对称Friedel-Crafts烷基化反应.金属铟(III)盐和手性磷酸组成的双酸催化体系可以高效、高选择性地催化吲哚与β,γ-不饱和α-酮酸酯的Friedel-Crafts烷基化反应.简单改变铟(III)盐的抗衡阴离子从F-到Br-,就能使产物的构型发生反转,并同时获得相应的高产率(最高达98%)和高对映选择性(最高大于99%)的1,4-加成产物.     

吲哚与硝基烯的Friedel-Crafts反应的研究进展

吲哚作为核心结构广泛存在于生物碱和药物中,吲哚衍生物在生物体的生理活动中起着重要的作用,其中吲哚和硝基烯的Friedel-Crafts是生成吲哚衍生物的重要方法.按照反应中催化剂种类的不同分为:(1)无催化剂,(2)离子液体催化剂,(3)金属盐催化剂,(4)配合物催化剂,(5)Br nsted酸催化剂,(6)有机小分子催化剂,(7)其他类型催化剂.对吲哚与硝基烯的Friedel-Crafts反应的情况进行了综述.     

Stereoselective Lewis acid-catalyzed alpha-acylvinyl additions

Silyloxyallenes derived from alpha-hydroxypropargylsilanes undergo efficient addition to aldehydes with catalytic amounts of Lewis acids. The allenes are accessed from the corresponding propargylsilanes in a base-catalyzed 1,2-Brook rearrangement/SE2' process. Enantioenriched propargylsilanes are synthesized by a new zinc-promoted addition of alkynes to acylsilanes in up to 74% ee. This work demonstrates that conversion to the silyloxyallenes occurs with minimal erosion in optical activity. The use of a chiral chromium(III) Lewis acid effects the catalytic asymmetric addition of racemic silyloxyallenes to aromatic aldehydes in up to 92% ee. The overall reaction is broad in scope and accommodates a wide variety of aromatic and aliphatic substituents on both the propargylsilane and aldehyde.     

Catalytic addition methods for the synthesis of functionalized diazoacetoacetates and application to the construction of highly substituted cyclobutanones

[reaction: see text] Methyl 3-(trialkylsilanyloxy)-2-diazo-3-butenoate undergoes Lewis acid-catalyzed Mukaiyama aldol addition with aromatic and aliphatic aldehydes in the presence of low catalytic amounts of Lewis acids in nearly quantitative yields. Scandium(III) triflate is the preferred catalyst and, notably, addition proceeds without decomposition of the diazo moiety. Diazoacetoacetate products from reactions with aromatic aldehydes undergo rhodium(II)-catalyzed ring closure to cyclobutanones with high diastereocontrol. Examples of complimentary Mannich-type addition reactions with imines are reported.     

CeO2-MnOx催化剂上氯乙烯有机废气的催化燃烧

采用柠檬酸(CA)溶胶-凝胶法制备了不同Mn:(Ce+Mn)摩尔比的CeO2-MnOx催化剂,以氯乙烯有机废气的催化燃烧为模型反应,考察了催化剂制备条件和反应条件对于CeO2-MnOx催化剂性能的影响,并用N2吸附、X射线衍射(XRD)和H2程序升温还原(H2-TPR)对催化剂进行了表征.结果表明,CeO2-MnOx催化剂上氯乙烯燃烧反应产物只有HCl,H2O和CO2,没有检测到其他氯代烃和氯气等副产物.当CA:Mn:Ce=0.3:0.50:0.50时,所制备的CeO2-MnOx催化剂活性最高,对于较宽的空速范围(10000～30000h-1)和较宽的浓度范围(0.05%～0.15%),低浓度氯乙烯的催化燃烧反应具有较好的操作弹性.其中当氯乙烯浓度为0.1%,空速为15000h-1时,起燃温度T50=110oC,完全转化温度T99=220oC.XRD和H2-TPR结果表明,在CeO2-MnOx催化剂中只出现立方相萤石结构CeO2的特征衍射峰,没有出现MnOx物种的特征衍射峰;Mn离子进入CeO2晶格形成的Ce-Mn-O固溶体,有利于提高催化剂表面的活性氧物种的活性,乃至催化剂活性.     

Lewis base activation of lewis acids. Addition of silyl ketene acetals to aldehydes

The weak Lewis acid silicon tetrachloride can be activated by catalytic amounts of the chiral bisphosphoramide (R,R)-3 to form a highly reactive, chiral trichlorosilyl cation which is an extremely effective promoter of aldol addition reactions between aldehydes and silyl ketene acetals. The tert-butyldimethylsilyl ketene acetal of methyl acetate adds nearly instantaneously to aromatic and olefinic aldehydes as well as aliphatic aldehydes (albeit more slowly) with excellent enantioselectivity. The homologous tert-butyldimethylsilyl ketene acetal of tert-butyl propanoate adds with nearly exclusive anti diastereoselectivity to a similar range of aldehydes also with excellent enantioselectivity. The origin of the slower reaction rate with aliphatic aldehydes is revealed to be the formation of chlorosilyl ether adducts.     

Highly enantioselective addition of in situ prepared arylzinc to aldehydes catalyzed by a series of atropisomeric binaphthyl-derived amino alcohols

The direct addition of in situ prepared arylzinc to aldehydes with chiral binaphthyl-derived amino alcohols as catalysts can afford optically active diarylmethanols in high yields and with excellent enantioselectivities (up to 99 % ee, ee = enantiomeric excess). By using a single catalyst, both enantiomers of many pharmaceutically interesting diarylmethanols can be obtained by the proper combination of various arylzinc reagents with different aldehydes; this catalytic system also works well for the phenylation of aliphatic aldehydes to give up to 96 % ee.     

Direct catalytic enantio- and diastereoselective aldol reaction of thioamides

A direct catalytic asymmetric aldol reaction of thioamides using a soft Lewis acid/hard Br?nsted base cooperative catalyst comprising (R,R)-Ph-BPE/[Cu(CH(3)CN)(4)]PF(6)/LiOAr is described. Exclusive enolate generation from thioacetamides through a soft-soft interaction with the soft Lewis acid allowed for a direct aldol reaction to α-nonbranched aliphatic aldehydes, which are usually susceptible to self-condensation under conventional basic conditions. A hard Lewis basic phosphine oxide has emerged as an effective additive to constitute a highly active ternary soft Lewis acid/hard Br?nsted base/hard Lewis base cooperative catalyst, enabling a direct enantio- and diastereoselective aldol reaction of thiopropionamides. Strict control of the amount of the hard Lewis base was essential to drive the catalytic cycle efficiently with a minimized retro-aldol pathway, affording syn-aldol products with high stereoselectivity. Divergent transformation of the thioamide functionality is an obvious merit of the present aldol methodology, allowing for a facile transformation of the aldol product into the corresponding aldehyde, ketone, amide, amine, and ketoester. An aldehyde derived from the direct aldol reaction was subjected to a second direct aldol reaction, which proceeded in a catalyst-controlled manner to provide 1,3-diols with high stereoselectivity.     

Rational design of sterically and electronically easily tunable chiral bisimidazolines and their applications in dual Lewis acid/brønsted base catalysis for highly enantioselective nitroaldol (Henry) reactions

A new addition to the rational design of sterically and electrically easily tunable chiral bis(imidazoline) ligands from chiral amino alcohols has been developed. Vast structural variation of chiral bis(imidazoline) ligands can be simply achieved by the choice of both the 1,2‐amino alcohol and its N‐1 R¹ substituent. A small library of chiral bisimidazolines ( 1 a – h ) has been constructed. The method has provided an easy and simplified route to a diverse set of air‐stable and water‐tolerant chiral bis(imidazoline) ligands on 10 g scales. The dual Lewis Acid/Brønsted base catalytic system generated from the (S)‐ 1 a /Cu(OTf)₂ complex and Et₃N was able to catalyze Henry reactions between aldehydes and nitromethane effectively at room temperature, and also to tolerate a wide scope of aldehydes with excellent enantiomeric excesses. Not only aromatic aldehydes but also aliphatic aldehydes afforded the nitroalcohol products, with enantiomeric excesses in the 93–98 % range. This dual catalytic system is among the most effective systems so far reported for the asymmetric parent Henry reactions. This work also represents the first members of the class of chiral bisimidazolines to have been demonstrated to achieve excellent enantioselectivities.     

The use of bifunctional catalyst systems in the asymmetric addition of alkynylzinc to aldehydes

The bifunctional ligand 2a showed a more enhanced reactivity than that of the corresponding amino alcohol ligand in the asymmetric addition of alkynylzinc to benzaldehyde. The bifunctional ligand 2a can catalyze the addition of phenylacetylene to various types of aldehydes including aromatic aldehydes, aliphatic aldehydes, and α,β-unsaturated aldehydes with high enantioselectivity (81–98% ee). The conditions of this catalytic process are both mild and simple.     

A Lewis acid-promoted cyclization of ethenetricarboxylate derivative aromatic compounds. Novel syntheses of oxindoles and benzofuranones via Friedel-Crafts intramolecular Michael addition

A novel cyclization reaction of ethenetricarboxylate derivative aromatic compounds in the presence of various Lewis acids gave benzo-annulated cyclic compounds such as oxindole and benzofuran derivatives via Friedel-Crafts intramolecular Michael addition in high yields. For example, the reaction of diethyl 2-[(N-methyl-N-phenylcarbamoyl)methylene]malonate (1a) in the presence of ZnCl2 at room temperature gave diethyl 2-(1-methyl-2-oxoindolin-3-yl)malonate (2a) in 98% yield. The reactions also proceeded with a catalytic amount of a Lewis acid such as AlCl3, ZnCl2, ZnBr2, Sc(OTf)3, or InBr3.     

Enantioselective cyanosilylation of ketones by a catalytic double-activation method with an aluminium complex and an N-oxide

Double-activation catalysis promises high catalytic efficiency in the enantioselective cyanosilylation of ketones through the combined use of a Lewis acid and a Lewis base. Catalyst systems composed of a chiral salen-Al complex and an N-oxide have high catalytic turnovers (200 for aromatic ketones, 1000 for aliphatic ones). With these catalysts, a wide range of aliphatic and aromatic ketones were converted under mild conditions into tertiary cyanohydrin O-TMS ethers in excellent yields and with high enantioselectivities (94% ee for aromatic ketones, 90% ee for aliphatic ones). Preliminary mechanistic studies revealed that the salen-Al complex played the role of a Lewis acid to activate the ketone and the N-oxide that of a Lewis base to activate TMSCN; that is, double activation.