Sulfonimidamide as a directing agent for Pd-catalyzed regioselective oxidative C–H acyloxylation of arenes

In this report, we describe the utilization of sulfonimidamide (SIA) as a novel directing group for a Pd-catalyzed regioselective oxidative C–H acyloxylation of aryl group of N-aroyl part of SIA in moderate to good yields in the presence of (Diacetoxyiodo)benzene (PhI(OAc)₂) as an oxidizing agent and alkanoic acid as solvent. The solvent alkanoic acid is found to be the source of acyloxylation.     

二十面体碳硼烷的亲电取代定位效应理论研究

利用Ｇａｕｓｓｉａｎ９４从头计算程序在６－３１Ｇ基组下对二十面体碳硼烷Ｃ２Ｂ１０Ｈ１２、ＣＢ１１Ｈ１２＾－及其衍生物ＣＢ１１Ｈ１１Ｂｒ＾－进行了从头计算，结果表明，在亲电取代反应中，杂原子Ｃ具有对、空间定位效应，取代基－Ｂｒ为邻，对位定位基因，与实验事实相符。     

Alkynylcyclohexadienyl tricarbonyliron complexes: A new directing effect for organoiron-mediated synthesis

The first example of an alkyne-substituted tricarbonyl(η⁵-cyclohexadienyl)iron(1+) complex has been prepared and the ω directing effect of the phenylethynyl substituent has been demonstrated in nucleophile addition reactions. Addition of NC⁻ also occurs at the a position to form an unusual η¹, η³-structure.     

L沸石导向剂陈化机制的研究

应用核磁共振和拉曼光谱研究了L沸石导向剂的陈化机制。实验结果表明,当铝源与硅源混合后铝酸根离子与硅酸根离子之间聚合反应很快,同时高聚态硅酸根离子发生了解聚。L沸石导向剂陈化反应的控制步骤是低聚态硅铝酸根离子之间或低聚态硅铝酸根离子与低聚态硅酸根离子之间的定向聚合反应。     

Ether-directed palladium(II)-catalysed aza-Claisen rearrangements: studies on the origin of the directing effect

Four new chiral δ-substituted allylic trichloroacetimidates have been synthesised to probe the origin of the high diastereoselectivity observed for the MOM-ether directed palladium(II)-catalysed aza-Claisen rearrangement. Rearrangement of these compounds has not only provided strong evidence for this directing effect but also that during the rearrangement both oxygen atoms from the MOM-ether are involved in coordinating to and directing the palladium(II) catalyst.     

A Sterically Tuned Directing Auxiliary Promotes Catalytic 1,2-Carbofluorination of Alkenyl Carbonyl Compounds**

The site-selective palladium-catalyzed three-component coupling of unactivated alkenyl carbonyl compounds, aryl- or alkenylboronic acids, and N-fluorobenzenesulfonimide is described herein. Tuning of the steric environment on the bidentate directing auxiliary enhances regioselectivity and facilitates challenging C(sp³)−F reductive elimination from a Pd^IV intermediate to afford 1,2-carbofluorination products in moderate to good yields.     

Steric redirection of alkylation in 1H-pyrazole-3-carboxylate esters

The alkylation of ethyl 1H-pyrazole-3-carboxylate with a variety of alkylating agents in the presence of K₂CO₃ was found to largely favor the formation of ethyl 1-substituted pyrazole-3-carboxylates. The alkylation could be sterically redirected by the use of a triphenylsilyl group (ethyl 3-(triphenylsilyl)-1H-pyrazole-5-carboxylate) to provide synthetically useful yields of ethyl 1-substituted-3-(triphenylsilyl)-1H-pyrazole-5-carboxylates. The triphenylsilyl group could be removed with Bu₄NF. Other triorganosilyl groups (TMS, TES, TBDMS) failed to provide significant redirection, while TIPS proved refractory to protodesilylation.     

Copper(II)-catalyzed direct thiolation of C–H bonds in aromatic amides with aryl and aliphatic thiols

An efficient approach for Cu-catalyzed thiolation of C_sp2–H bonds of directing-group-containing aromatic amides with 1°, 2°, and 3° aliphatic thiols and thiophenols has been developed. This method shows excellent functional group tolerance and provides a straightforward way for the preparation of aryl thioethers.     

Directing/protecting groups mediate highly regioselective glycosylation of monoprotected acceptors

A directing/protecting group designed for regioselective functionalization of partially-protected glucopyrannosides has been successfully used to prepare disaccharides in high yields. Most importantly, it has been demonstrated that highly regioselective and stereoselective glycosylation can be achieved when disarmed donors are employed. This study demonstrates the ability of directing/protecting group to induce regioselective glycosylation of carbohydrates and opens the field to the design of other DPGs for other monosaccharides.     

Metal-Free Directed Site-Selective Csp3-H Borylation of Saturated Cyclic Amines

The borylation of Csp³−H bonds is a challenging transformation that is typically restricted to transition metal catalysis. Herein, we report the site-selective metal-free Csp³−H borylation of saturated cyclic amines. It is possible to selectively borylate piperidine derivatives at the α or β positions according to the reaction conditions. The mechanism was supported by NMR spectroscopy, calorimetry experiments and density functional theory (DFT) computations. It suggests that the piperidine is dehydrogenated by complexation with BBr₃ to produce an enamine intermediate, which is in turn borylated at either the α or β position according to the reaction conditions.     

Transition metal-catalyzed α-alkylation of amines by C(sp3)‒H bond activation

α-Substituted amines are present in a myriad of biologically active natural and synthetic products. With the objective of developing atom-economical reactions, a panel of synthetic methods allowing the direct functionalization of C(sp³)?H bonds adjacent to the nitrogen atom have been developed. The field remains dominated by the sequence α-lithiation/addition on an electrophile even if the use of reactive organolithium reagents is not compatible with all functional groups. Over the past ten years, an increasing interest has been devoted to metal-catalyzed CH-activation, some studies being specially dedicated to C(sp³)?H bond activation. Notably, this approach has been envisioned to perform direct α-functionalization of amines. The aim of this article is to give an overview of synthetic methods for transition metal-catalyzed α-alkylation of amines by C(sp³)?H bond activation.     

Cu-catalyzed direct ortho-chlorination/-oxygenation of aryls: Switching of oxidant,control the diversity of products

Highly regioselective copper catalyzed ortho-chlorination of aryl pyridines was achieved with TBHP as oxidant and 1,2-dichloroethane as chlorinating agent for the first time. Switching the oxidant from TBHP to benzoyl peroxide under identical reaction conditions effects ortho-oxygenation.     

Enantioselective Hydroalkenylation and Hydroalkynylation of Alkenes Enabled by a Transient Directing Group: Catalyst Generality through Rigidification**

The catalytic enantioselective synthesis of α-chiral alkenes and alkynes represents a powerful strategy for rapid generation of molecular complexity. Herein, we report a transient directing group (TDG) strategy to facilitate site-selective palladium-catalyzed reductive Heck-type hydroalkenylation and hydroalkynylation of alkenylaldehyes using alkenyl and alkynyl bromides, respectively, allowing for construction of a stereocenter at the δ-position with respect to the aldehyde. Computational studies reveal the dual beneficial roles of rigid TDGs, such as L-tert-leucine, in promoting TDG binding and inducing high levels of enantioselectivity in alkene insertion with a variety of migrating groups.     

Palladium-catalyzed reactions of cyclopropanols bearing oxazoline directing group

Cyclopropanols bearing oxazoline directing group were investigated in palladium-catalyzed reactions. When the directing group and cyclopropanol unit were bonded through two- or three-carbon spacer, formation of unusual products was observed. Oxidative ring opening proceeded with uncommon regioselectivity providing linear enones as main products. The reaction of such cyclopropanols with aryl iodides and silver acetate furnished diarylated α-methylene ketones, which cannot be obtained from cyclopropanols lacking oxazoline ring under the same conditions.     

高硅Y沸石的合成研究进展

Y沸石的合成及在流化催化裂化中的应用在现代石油化学工业中具有里程碑意义. Y沸石的骨架硅铝比直接影响材料的热/水热稳定性及催化性能. 提高Y沸石的骨架硅铝比、 合理减少酸中心密度、 提高酸强度, 进而改善催化裂化反应性能一直是学术界和工业界关注的重要课题. 目前工业使用的高硅Y沸石均是通过复杂的后处理方法获得的. 与复杂的后处理方法相比, 直接合成高硅Y沸石是更理想的方式, 但其难度大, 为分子筛领域具有挑战性的课题. 本文系统总结了高硅Y沸石的直接合成研究进展, 分别对无机合成体系和有机模板剂合成体系进行综合评述, 并介绍了Y沸石的晶化机理研究进展.     

Studies on the aza-Claisen rearrangement of 4,5-dihydroxylated allylic trichloroacetimidates: the stereoselective synthesis of (2R,3S)- and (2S,3S)-2-amino-3,4-dihydroxybutyric acids

Two new synthetic approaches, involving substrate directed aza-Claisen rearrangements and aza-Claisen rearrangements mediated by chiral Pd(II) catalysts, have been developed for the stereoselective synthesis of (2R,3S)-2-amino-3,4-dihydroxybutyric acid, a dihydroxylated α-amino acid from the edible mushroom, Lyophyllum ulmarium and its (2S,3S)-unnatural diastereomer.     

Pd(II)-catalyzed cascade Heck/intramolecular C(sp2)–H amidation reaction: An efficient route to 4-aryl-2-quinolinones

A Pd(II)-catalyzed cascade Heck/intramolecular C(sp²)–H amidation reaction is described for the synthesis of 4-aryl-2-quinolinone derivatives. Substituted cinnamamide containing 2-(pyridin-2-yl)ethanamine unit reacts with aryl iodide to form intermediate by Heck reaction. Then, the intermediate takes place intramolecular amidation via C(sp²)–H activated process promoted by orientation group.     

The Role of Sulphonamides and N-Sulphonyl Ketimines/Aldimines as Directing Groups in the Field of C−H Activation

Sulphonamides and N-sulphonyl ketimines/aldimines have turned out to be versatile motifs in the field of synthetic and medicinal chemistry. The field of C−H activation/functionalization flourished remarkably due to their synthetic applicability and directing group plays a remarkable role to achieve regioselectivity in these reactions. The current review summarizes recent tactics by utilizing sulphonamides and N-sulphonyl ketimines/aldimines as directing groups for C−H activation or functionalization. As a directing group, they also facilitate site selectivity and late-stage functionalization of drug molecules in order to construct complex scaffolds of therapeutic importance by C−H activation.     

Facile Synthesis of Alkylidene Phthalides by Rhodium-Catalyzed Domino C−H Acylation/Annulation of Benzamides with Aliphatic Carboxylic Acids

The Rh-catalyzed ortho-C(sp²)−H functionalization of 8-aminoquinoline-derived benzamides with aliphatic acyl fluorides generated in situ from the corresponding acids has been developed. This reaction initiated with 8-aminoquinoline-directed ortho-C(sp²)−H acylation, which was accompanied by subsequent intramolecular nucleophilic acyl substitution of amide group to produce alkylidene phthalides This approach exhibits high stereo-selectivity for Z-isomer products, and tolerates a variety of functional groups as well as aliphatic carboxylic acids with diverse structural scaffolds.     

Studying competitive lithiations at alpha-, ortho-, and benzylic positions in various N-protected aniline derivatives

The directing effects of the t-BuOCONH- (NHBoc) and the t-BuCONH- (NH-pivaloyl) groups have been investigated on a series of differently substituted anilines. Depending on the nature of the directing group and the substrate, lithiation either occurred in the ortho-, benzylic-, or alpha-position. In general, it was observed that ortho-lithiation is the least facile process and alpha-lithiation slightly favored compared to lithiation in the benzylic position. However, it was found that minor changes in the starting materials led to different regioselectivity in the metalation process. For example, changing substituents from methyl to ethyl can result in completely different regioselectivity. As final conclusion, a graphical guideline for lithiation experiments is presented.