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Aromatic compounds are omnipresent in organic chemistry, which are the broadest skeletons of bioactive molecules, medicines, and materials. Due to their importance, conventional methods to assemble aromatic rings have attracted considerable attention. The direct formation of benzene cores from readily available acyclic precursors offers a highly versatile and superior approach to prepare both small organic molecules and sophisticated natural products. Recently, organocatalyst‐mediated annulation reaction, including phosphine‐, tertiary amine‐, secondary amine‐, primary amine‐, and NHC‐mediated benzannulation reactions, is considered as an efficient method to access multi‐substituted arenes. In this review, we will emphasize the selected exa.
A highly enantioselective intramolecular NHC‐catalyzed approach for the synthesis of benzo‐fused pyranones bearing quaternary stereocenter is described. The developed methodology is based on annulation reaction between acyl anion intermediates and β,β‐disubstituted Michael acceptors. The reaction offers streamlined and effective access to target products in. a highly stereoselective manner.
Electrochemically induced radical‐initiated reaction of vinyl azides with N ‐hydroxyphthalimide resulting O ‐phthalimide oximes with challenging for organic chemistry N‐O‐N fragment has been discovered. The developed approach introduces in synthesis electrochemically generated O‐centered imide‐ N ‐oxyl radicals as the coupling components. Sequential formation of C‐O and N‐O bonds was achieved via generation and selective addition of imide‐ N ‐oxyl radicals, followed by recombination with iminyl radicals. A wide range of O ‐phthalimide oximes was obtained with the yields up to 84%.
This review highlights the most significant advances that were accomplished in the chemistry of azolium‐carboxylate betaines within the years 2009–2020. Whenever needed, prior, seminal achievements are also briefly recalled to help put recent developments in a broader perspective. The compounds under scrutiny are zwitterions obtained upon nucleophilic addition of N heterocyclic carbenes (NHCs) onto carbon dioxide. We first present an overview of the various synthetic paths that give access to these inner salts before discussing their stability. The main part of this report then summarizes the numerous applications relying on NHC·CO2 zwitterions —employed either in stoichiometric or catalytic proportions— in the fields of organometallic chem.
NHC‐Nickel(0) catalyzed 1,3‐ and 1,4‐diastereodivergent hydroacylative heteroenyne cyclization with aldehydes was achieved (Syn‐:Anti‐, switchable from up to 1:99 to 98:2). Both sets of heterocyclic diastereomers are accessible via this route, with a high γ‐:α‐enone structure ratio. Preliminary DFT investigations indicated that the manipulation of the N‐substituent exerts a direct influence on the diastereoselectivity of NHC‐nickelacyclopentene formation. The energy differences associated with the endocyclic bond angle (C‐Z‐C) changes noted in the calculations, might possibly account for the broad scope and high diastereodivergent selectivity observed.
The efficient and enantioselective construction of cyclic compounds with a halogenated tetrasubstituted carbon through various catalytic strategies remains challenging. Thus, research on modern asymmetric catalysis is important. In this review, recent achievements that streamlined the synthesis of halogenated cyclic molecules through organocatalysis or transition‐metal catalysis were introduced.
In the last 20 years, efficient transition metal catalysts for the α‐arylation of enolates have been introduced. Despite the popularity and utility of these reactions, there remains room for improvement (reduced costs, elimination of transition metals and specialized ligands). Herein is reported a general, scalable and green method for aroylation of simple diarylmethane pronucleophiles through direct acyl C–N cleavage of N‐Bn‐N‐Boc arylamides and N‐acylpyrroles under transition metal‐free conditions. Importantly, a 1 : 1 ratio of the amide to the pronucleophile is employed. Unlike. use of Weinreb amides, this method avoids preformed organometallics (organolithium and Grignard reagents) and does not employ cryogenic temperatures, which are d.
Tunable catalytic annulation reactions of βalkynyl ketones with indoles have been developed, enabling multiple chemical bond‐forming events to selectively access skeletally diverse indole‐containing heterocycles with generally good yields. Silver‐catalyzed intermolecular benzannulation reaction of β‐alkynyl ketones with indoles afforded tetracyclic benzo[b]carbazoles whereas isochromen‐1‐yl‐substituted indoles could be obtained using the same silver catalysis by lowering the reaction temperature (0 oC or rt). Interestingly, using Sc(OTf)3 and AgOTf as a combined catalytic system led to the formation of C3‐naphthylated indoles via intramolecular benzannulation reaction.
Sulfur‐containing skeletons are widely found in natural products, drugs and bioactive compounds. As a direct and efficient access to sulfur‐functionalized carbon stereocenters, the catalytic enantioselective reactions of sulfur‐containing prochiral carbon centers have attracted great attention in the past few years. The review summarizes the chemistry of thiazolones, rhodanines and their derivatives in the context of catalytic enantioselective construction of sulfur‐containing skeletons. 1 Introduction. 2 Reactions of 4H‐thiazol‐5‐ones. 2.1 Mannich‐type reaction. 2.2 Conjugate addition. 3 Reactions of 5H‐thiazol‐4‐ones. 3.1 Conjugate addition. 3.2 Mannich‐type reaction. 3.3 Allylation. 3.4 Propargylation. 4 Reactions of rhodanines. 4.1 Conjugate addi.
Abstract. The use of formate dehydrogenases (FDHs) for regeneration of the important cofactor NADH in enzyme‐catalysed synthetic reactions has several advantages over alternative systems. However, a major bottleneck for broad industrial applications is the low specific activity of the currently used FDHs. In this study, we introduce a novel NAD‐dependent formate dehydrogenase from Rhodococcus jostii (RjFDH) with both high specific activity and stability. The enzyme was identified in a targeted database research and recombinantly obtained from Escherichia coli. RjFDH is a homodimer with a monomeric molecular mass of 44.7 kDa. The homology model shows that all amino acid residues of the NAD‐dependent formate dehydrogenases are usually concern.
A palladium‐catalyzed [2 + 2 + 1] annulation among 3‐iodochromones, benzyl bromides, and norbornene has been developed. This annulation consists of a domino sequence involving Heck coupling/C(sp2)−H activation/C(sp3)−H activation, affording a variety of complex chromone derivatives bearing five contiguous tertiary carbon centers in up to 94% yield and 99:1 dr. Interestingly, the diastereoselectivity could be switched by fine‐tuning the solvent, in which endo isomer and exo isomer were obtained using mesitylene/CH3CN and mesitylene, respectively.
The Friedel‐Crafts reaction represents one of the most efficient tools for the formation of carbon‐carbon bonds and direct derivatization of aromatic compounds. Asymmetric arylation of imines involving Friedel‐Crafts reaction has received much interest recently. The present review summarizes the works on the asymmetric arylation of imines by different approaches including Friedel‐Crafts reaction and their development to date. The review is divided into three main sections: addition reaction of arenes to imines in the presence of chiral catalysts; addition reaction of arenes to imines containing chiral tails and asymmetric coupling reaction of aryl boronic acids and imines.
A palladium‐catalyzed external‐CO‐free carbonylative Hiyama‐Denmark cross‐coupling reaction is presented. The introduction of silylcarboxylic acids as bifunctional reagents (CO and nucleophile source) avoids the need for external gaseous CO and a silylarene coupling partner. The transformation features high functional group tolerance and it is successful with electron‐rich, ‐neutral, and ‐poor aryl iodides. Stoichiometric studies and control experiments provide insight into the reaction mechanism and support the hypothesized dual role of silylcarboxylic acids.
Addition to prochiral cyclic 1,3‐diketones applying bifunctional Cinchona‐derived squaramides resulted in chiral adducts with stereoselectivities of up to 99% ee and allowed for desymmetrization of nucleophile. These labile hemiacetal intermediates were transformed to new 1,4‐dihydropyridines with high diastereoselectivities and no erosion of optical purity. Their further oxidation to pyridine followed by Fisher indolization provided the chiral pyridine‐indoles.
A novel planar chiral dirhodium paddlewheel complex Rh2(Sp‐PCP)4 based on the [2.2]paracyclophane has been synthesized for the challenging cyclopropanation of alkene derivatives with tert‐butyl α ‐diazo propionates. The homobimetallic rhodium catalyst relies on the high steric demand and rigidity of [2.2]paracyclophane that favors the cyclopropanation of 1‐aryl substituted, 1,1‐disubstituted and benzannulated alkenes over β‐hydride migration at room temperature with high diastereoselectivity.
An organobase‐controlled, divergent cascade reaction to construct spirocyclohexene indane‐1,3‐diones and coumarin‐fused cyclopentanes is reported. The cascade reaction is triggered by the 1,6‐addition of 3‐homoacylcoumarins to the indanedione‐derived acceptors and further regio/chemoselective reaction that preferentially resulted in spiro systems and fused cyclopentanes in a diversity‐oriented manner. The 1,6‐addition/aldol and 1,6‐addition/vinylogous Michael addition cascade processes were controlled by different base/solvent systems to the predominant formation of one of the two carbocyclic compounds.
An intermolecular aza‐Wacker‐type reaction was developed. When a readily available olefin was treated with a nitrogen nucleophile in the presence of a Pd–SPRIX complex and potassium persulfate, allylamine derivatives were obtained with high yield and excellent regioselectivity. The mechanistic studies showed that the reaction followed first‐order dependence on the olefin as well as palladium catalyst, but zero‐order dependence on the nitrogen nucleophile.
Substituted oxabicyclo derivatives bearing two quaternary carbon centers and five contiguous stereocenters have been synthesized from C3‐thioester/‐ester substituted dienones, a simple and linear pluripotent molecular platform. The conversion proceeds from neat reactants, possibly via a thermally‐driven pericyclic cascade manifold involving sequential (E)‐s‐trans to (E)‐s‐cis isomerization, oxa‐6π‐electrocyclization, and intermolecular, regioselective [4π + 2π] cycloaddition. The proposed mechanism has been substantiated by intermediate trapping experiments and DFT studies. Such dienones have also been exploited to effect stereoselective cross Diels‐Alder cycloadditions with olefins and sequential Diels‐Alder/retro‐Diels‐Alder reactions wit.

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