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Configurationally‐defined dienes are pervasive across the bioactive natural product spectrum, where they typically manifest themselves as sorbic acid‐based fragments. These C5 motifs reflect the biosynthesis algorithms that facilitate their construction. To complement established biosynthetic paradigms, a chemical platform to facilitate the construction of stereochemically defined, functionalizable dienes by light‐enabled isomerization has been devised. Enabled by selective energy transfer catalysis, a variety of substituted β‐boryl sorbic acid derivatives can be isomerized in a regio‐ and stereo‐selective manner (up to 97 : 3). Directionality is guided by a stabilizing nO→pB interaction in the product: this constitutes a formal anti‐hydroboration of the starting alkyne. This operationally simple reaction employs low catalyst loadings (1 mol %) and is complete in 1 h. X‐ray analysis supports the hypothesis that the nO→pB interaction leads to chromophore bifurcation: this provides a structural foundation for selective energy transfer. [ABSTRACT FROM AUTHOR]

Because internal alkenes are more challenging synthetic targets than terminal alkenes, metal‐catalyzed olefin mono‐transposition (i.e. positional isomerization) approaches have emerged to afford valuable E‐ or Z‐ internal alkenes from their complementary terminal alkene feedstocks. However, the applicability of these methods has been hampered by lack of generality, commercial availability of precatalysts, and scalability. Here, we report a nickel‐catalyzed platform for the stereodivergent E/Z‐selective synthesis of internal alkenes at room temperature. Commercial reagents enable this one‐carbon transposition of terminal alkenes to valuable E‐ or Z‐internal alkenes via a Ni−H‐mediated insertion/elimination mechanism. Though the mechanistic regime is the same in both systems, the underlying pathways that lead to each of the active catalysts are distinct, with the Z‐selective catalyst forming from comproportionation of an oxidative addition complex followed by oxidative addition with substrate and the E‐selective catalyst forming from protonation of the metal by the trialkylphosphonium salt additive. In each case, ligand sterics and denticity control stereochemistry and prevent over‐isomerization. [ABSTRACT FROM AUTHOR]

This article discusses the development of sustainable catalytic chemical methods for O-glycosylation using iron-based salts as catalysts. The authors experiment with different reaction conditions and optimize the yield of the glycosylation reaction. The study demonstrates the potential of iron-based salts as a sustainable and affordable alternative for large-scale synthesis. The article provides detailed information about the synthesis and characterization of various compounds, including their yields, physical properties, and spectroscopic data. This information can be useful for researchers studying organic chemistry or interested in the synthesis and characterization of specific compounds. [Extracted from the article]

The hydrogen bond (HB) catalysed Diels-Alder (DA) reactions of acrolein with cyclopentadiene have been investigated within the Molecular Electron Density Theory (MEDT) at the ωB97X-D/6-311G(d,p) computational level. The formation of HBs increases the electrophilicity of these species, suggesting an acceleration of these polar Diels-Alder (P-DA) reactions with forward electron density flux. Formation of one or two HBs with acrolein decreases the activation energies of the HB-catalysed P-DA reactions by 1.7 (methanol) and 4.0 (squaramide) kcal·mol−1, with the corresponding DA reactions exhibiting low endo stereoselectivity. These HB-catalysed DA reactions proceed through non-concerted one-step mechanisms via asynchronous transition state structures (TSs). An Interacting Quantum Atoms (IQA) energy partitioning analysis of the TSs indicates that the intra-atomic stabilization of the acrolein framework, coupled with the increase of the global electron density transfer, plays a crucial role in reducing the activation energies of these HB-catalysed DA reactions.

The development of the merger of a Ni(II) catalyst with an appropriate photocatalyst under visible‐light irradiation provides a new strategy for realizing direct functionalization of C(sp3)−H bonds. Mechanistically, whether the reduction of Ni catalyst to form a Ni(0) species is necessary in the dual catalysis still remains under debate. Herein, DFT calculations were carried out to gain a mechanistic insight into the enantioselective acylation of α‐amino C(sp3)−H bonds to furnish α‐amino ketones via photoredox and Ni dual catalysis. A feasible mechanistic pathway for the Ni catalysis via the Ni(I)−Ni(III)−Ni(II)−Ni(III)−Ni(I) cycle is suggested with the sequential elementary steps of oxidative addition, single electron reduction, radical addition, and reductive elimination in leading to the final product, whereas a nickel catalytic cycle, Ni(I)−Ni(0)−Ni(II)−Ni(III)−Ni(I), might not be feasible for the photoredox and Ni dual‐catalyzed acylation of α‐amino C(sp3)−H bonds. The origin of the stereoselectivity for this reaction is also discussed, which could be attributed to the minimization of the steric hindrance between the alkyl moiety of radical part and phenyl group of the chiral ligand. [ABSTRACT FROM AUTHOR]

The strained/frustrated electrostatic interactions between the ion pair of TTBPy+ X– increases the reactivity in both the ions, resulting in the activation of a third molecule like sulfonamides (aromatic/-aliphatic) via hydrogen bonding. This intriguing weak-interactions-based reactivity has been utilized to develop an organocatalytic synthesis of 2-deoxy-sulfonamido-glycosides from glycals. The sulfonamidoglycosylation of glycals using a catalytic amount of 2,4,6-tri- tert -butylpyridinium salts proceeded stereoselectively to provide N -glycosides in good to high yields. This process was demonstrated with l -rhamnal and d -galactal. Besides, IR spectroscopic studies explain that the hindered protonated pyridine cannot behave as a cationic Brønsted acid as is generally perceived. [ABSTRACT FROM AUTHOR]

An operationally simple in situ protection/deprotection strategy that significantly expands the scope of kinetically controlled catalytic Z- and E-selective olefin metathesis is introduced. Prior to the addition of a sensitive Mo- or Ru-based complex, treatment of a hydroxy- or a carboxylic-acid-containing olefin with commercially available HB(pin) or readily accessible HB(trip)2 (pin=pinacolato, trip=2,4,6-tri(isopropyl)phenyl) for 15 min is sufficient for efficient generation of a desired product. Routine workup leads to quantitative deprotection. A range of stereochemically defined Z- and E-alkenyl chlorides, bromides, fluorides, and boronates or Z-trifluoromethyl-substituted alkenes with a hydroxy or carboxylic acid group were thus prepared in 51-97 % yield with 93 to >98 % stereoselectivity. We also show that, regardless of whether a polar functional unit is present or not, a small amount of HB(pin) may be used to remove residual water, significantly enhancing efficiency.

A novel enantiopure π‐allylruthenium(IV) precatalyst allowed the enantioselective and stereospecific allylations of indoles and gave access to indolin‐3‐ones, containing vicinal stereogenic centers. Facile separation of diastereoisomers exhibiting opposite circularly polarized luminescence (CPL) activities in diverse solvents, including water, demonstrated the potential of these sustainable transformations and of the newly prepared molecules. [ABSTRACT FROM AUTHOR]

While vinyl cyclopropanes are valuable functional groups in drugs or natural products as well as established precursors to trigger a rich variety of synthetic transformations, their reactive nature can make their installation via direct catalytic approaches challenging. We herein present a modular access to (di)vinyl cyclopropanes under very mild conditions and full conservation of stereochemistry, allowing access to the cis or trans cyclopropane‐ as well as E or Z vinyl‐stereochemical relationships. Our protocol relies on air‐stable dinuclear PdI catalysis, which enables rapid (<30 min) and selective access to a diverse range of vinyl cyclopropane motifs at room temperature, even on gram scale. [ABSTRACT FROM AUTHOR]

Alkene metathesis catalyzed by enantiopure metal alkylidene complexes enables exceptionally versatile strategies to products with configurationally‐defined stereocenters. Desymmetrization processes thereby provide reliable stereoselective routes to aliphatic structures, while the differentiation of aromatic stereogenic units remained an outstanding challenge. Herein, we describe the feasibility of alkene metathesis to catalytically control stereogenic axes by traceless arene formation. Stereodynamic trienes are selectively converted into corresponding binaphthalene atropisomers upon exposure to a chiral molybdenum catalyst. Remarkably, stereoselective arene‐forming metathesis allows enantioselectivities of up to 98 : 2 e.r. and excellent yields. As the disconnection of each bond of an aromatic target is retrosynthetically conceivable, it is anticipated that forging arenes by means of stereoselective metathesis will enable versatile approaches for the synthesis of a broad range of molecular topologies with precisely defined configuration. [ABSTRACT FROM AUTHOR]

• Mechanisms in isothiourea-catalyzed reaction between acetic ester and alkynyl imine has been systematically studied. • NCI and AIM analyses are performed to uncover the origin of stereoselectivity. • EPS analysis are employed to disclose the origin of chemoselectivity. Increasing attention is being paid to divergent chemical reactions as a strategy for synthesizing complex organic molecules simply by regulating and adjusting reaction conditions. However, the factors controlling this switchable transformation remain unclear. A systematic study was conducted using density functional theory (DFT) at the M06–2X level to determine the mechanism of an isothiourea-catalyzed divergent chemical reaction of an aryl acetic acid ester with an imine in different solvents (acetonitrile and ethanol). The origins of the stereoselectivity and chemoselectivity of the reaction were determined using noncovalent interaction (NCI) and electrostatic potential surface (EPS) analyses. Lactamization reaction occurs preferentially in acetonitrile, and esterification proceeds preferentially in ethanol. The reaction of an ammonium enolate intermediate with an alkynyl imine preferentially generates the SS -configured isomer. The results of this theoretical study provide insight into the general mechanism of isothiourea-catalyzed reactions in which the key intermediate is ammonium enolate. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] Biocatalysis is an important area of modern research and is extensively explored by various industries to attain greener methods in various applications. Supramolecular interactions of short peptides have been under the scanner for developing artificial smart materials inspired from natural systems. Peptide-based artificial enzymes have been proved to show various enzyme-like activities. Therefore, immobilization of catalytic peptides on solid surfaces can be an extremely useful breakthrough for development of cost-effective catalytic formulations. In this work, a series of peptide amphiphiles (PAs) have been systematically analyzed to find the most effective catalyst with esterase like activity. The PA, containing a catalytic triad, 'Asp(Ser)His' in a branched manner, was further immobilized onto silica nanoparticles through covalent bonding method to obtain surface coated catalytic silica nanoparticles. The heterogenous catalytic formulation not only showed enhanced esterase activity than the self-assembled PA in homogenous phase, but also exceeded the activity of natural CV lipase. The catalytic formulation showed high stereoselectivity towards chiral esters. Moreover, the catalyst remained stable at higher temperature, in presence of various denaturant and retained its activity after several catalytic cycles. The ease of separation, robust nature, reusability and high stereoselectivity of the catalyst opens up the possibility of creating new generation heterogeneous catalysts for further industrial applications. [ABSTRACT FROM AUTHOR]

Intermolecular photocatalytic hydroaminoalkylation (HAA) of alkenes have emerged as a powerful method for the construction of alkyl amines. Although there are some studies aiming at stereoselective photocatalytic HAA reactions, the alkenes are limited to electrophilic alkenes. Herein, we report a highly regio‐, diastereo‐, and enantioselective HAA of electron‐rich dienol ethers and α‐amino radicals derived from α‐amino acids using a unified photoredox and palladium catalytic system. This decarboxylative 1,2‐Markovnikov addition enables the construction of vicinal amino tertiary ethers with high levels of regio‐ (up to >19 : 1 rr), diastereo‐ (up to >19 : 1 dr), and enantioselectivity control (up to >99 % ee). Mechanistic studies support a reversible hydropalladation as a key step. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: The asymmetric reductive arylation and alkenylation of benzylic chloride under photoredox/nickel dual catalysis using chiral biimidazoline (BiIm) ligand is reported to access 1,1‐diaryl alkanes and aryl allylic compounds with good yield as well as stereo‐ and enantioselectivities. This protocol uses more commercially available and less expensive C(sp2)‐Br as the electrophile coupling partner. A primary result using alkenyl chloride and alkyl chloride is also reported. Various functional groups are tolerated and the applications of this method are investigated by late‐stage functionalization and gram‐scale reaction. [ABSTRACT FROM AUTHOR]

The stereochemical outcome of reactions of chiral nucleophilic trisubstituted acetonide radicals with electron-deficient alkenes is dictated by a delicate balance between destabilizing non-bonding interactions and stabilizing hydrogen-bonding between substituents on the α and β carbons.

Zhipeng Zhang (left) received his B.S. degree from Shandong University (China) in 2004, and his Ph.D. degree from the Shanghai Institute of Organic Chemistry (SIOC) in 2010 under the supervision of Professor Kuiling Ding. In 2011, he began his postdoctoral studies with Professor Benjamin List at the Max Planck Institute for Coal Research in Mülheim an der Ruhr, Germany. After three years of research on asymmetric organocatalysis, he joined the group of Professor Jin-Quan Yu at The Scripps Research Institute in La Jolla, California as a postdoctoral research associate in 2014. He subsequently worked at the Genomics Institute of the Novartis Research Foundation (GNF) from 2016, before he began his independent career as a professor at the East China University of Science and Technology (ECUST) in 2017. His current research interests include asymmetric catalysis and synthetic methodology, focusing on the design and development of novel chiral ligands and catalysts. Baoguo Zhao (right) received his B.S. degree from Wuhan University in 1996, his M.S. degree from Nanjing University under the supervision of Professor Jianhua Xu in 2002, and his Ph.D. degree from the Shanghai Institute of Organic Chemistry (SIOC) under the supervision of Professor Kuiling Ding in 2006. He subsequently worked with Professor Yian Shi for five years as a postdoctoral fellow at the Department of Chemistry of Colorado State University. In 2011, he joined Shanghai Normal University at the Department of Chemistry as a full professor. His current research interests are in the area of biomimetic asymmetric catalysis, including the development of bioinspired chiral catalysts and synthetic methodologies. [ABSTRACT FROM AUTHOR]

A comprehensive study on the influence of N‐substitution on the stereoselective outcome of the synthesis of 3‐methyleneisoindolin‐1‐ones from 3‐alkyl‐3‐hydroxyisoindolin‐1‐ones is reported. The study was performed on an array of structurally diverse 3‐alkyl‐3‐hydroxyisoindolin‐1‐ones with tunable sizes of N‐substituents. In a methanesulfonic acid‐catalyzed reaction, substrates without N‐substituent (N−H) afforded exclusively the Z‐isomer, while an increase in their size was followed by the formation of a stereoisomeric mixture with the E‐isomer as the major component. [ABSTRACT FROM AUTHOR]

An efficient and attractive Co/organophotoredox dual catalysis protocol has been developed allowing the stereoselective access to a wide variety of syn‐configured 1,3‐diols featuring quaternary carbon centers. The synthesis of the target molecules is achieved under ambient reaction conditions using modular and accessible reagents, substituted vinyl cyclic carbonates and aldehydes, and in short reaction times. Mechanistic control experiments suggest that the stereoselectivity can be rationalized via a preferred Zimmerman–Traxler transition state comprising a Co(allyl) species and an activated aldehyde. This newly developed process thus expands the use of base metal catalysis in the construction of challenging quaternary carbon stereocenters. [ABSTRACT FROM AUTHOR]

• Two mutants were designed to convert NBPO into (S) and (R)−NBPL respectively. • The catalytic efficiency of L34A/W116A was increased by 26.82-fold compared to the WT. • This integrated engineering avoids the trade-off between activity and stereoselectivity. Green and efficient biosynthesis of two enantiomeric products of N-Boc-pyrrolidinol (NPBL) as key pharmaceutical blocks for treatment of cancer and HIV has received much attention. The precursor, N-Boc-pyrrolidone (NPBO), is considered as a difficult-to-reduce ketone by carbonyl reductases, because it has a bulky Boc group and sterically similar substitutions on either side of the carbonyl group resulting in low stereoselectivity and conversion. Moreover, activity enhancement concomitant with reversal of stereoselectivity is challenging. Carbonyl reductase (CpCR) from Candida parapsilosis shows 90 %ee for (S)-NBPL, but low catalytic efficiency. In this study, we considered both activity and selectivity, and proposed an integrated engineering strategy. The distal site was introduced from an activity perspective and the active pocket sites were introduced by virtual saturation mutagenesis from a stereoselectivity perspective. Mutants L34A/W116A (95 %ee (S)) and L34A/W116T/F285C/W286S (94 %ee (R)) were obtained with 26.8-fold and 2.9-fold higher catalytic efficiencies, respectively. Molecular dynamics simulations revealed the mechanism of stereoselective flip-flop and activity enhancement; mutation altered the substrate-binding mode and changed the shape and size of the cavities, thus contributing to the change in the ratio of active conformations in the pre-reactive state. This study, which differs from the traditional method of exchanging large and small pockets, provides a viable approach for the rational design of carbonyl reductases with high stereoselectivity for target substrates. [Display omitted] [ABSTRACT FROM AUTHOR]

Main observation and conclusion: Stereoselective isomerization of α‐alkyl styrenes is accomplished using a new iron catalyst supported by phosphine‐pyridine‐oxazoline (PPO) ligand. The protocol provides an atom‐efficient and operationally simple approach to trisubstituted alkenes in high yields with excellent regio‐ and stereoselectivities under mild conditions. The results of deuterium‐labelling and radical trap experiments are consistent with an iron‐hydride pathway involving reversible alkene insertion and β‐H elimination. [ABSTRACT FROM AUTHOR]

The density functional theory (DFT) calculations were performed to gain insights into possible reaction mechanisms and origin of selectivities on phosphine catalyzed [2+3] and [2+4] annulations of saturated amine with allenoate for the first time. The computed results reveal that allenoate prefers to serve as a C3 synthon rather than C4 synthon under phosphine catalysis, and the whole catalytic cycle generally undergoes through eight processes, i. e. (1) adsorption of catalyst, (2) dissociation of AcO− group, (3) deprotonation of saturated amine, (4) nucleophilic attack by the deprotonated amine anion to the electrophilic phosphonium diene intermediate, (5) [1,6]‐proton shift, (6) ring closure of five‐membered heterocycle, (7) [1,2]‐proton shift, and (8) desorption of catalyst and the formation of 3‐pyrroline. The fourth step was identified as both chemo‐ and stereo‐selectivities determining step, and the pathway associated with R‐isomer is energetically favorable pathway. Further non‐covalent interaction (NCI) and Bader's atoms‐in‐molecules (AIM) analysis reveal that the C−H⋅⋅⋅O interaction has a significant contribution to the stability of R‐configured transition state. The obtained insights should be valuable for understanding the general principle for the detailed mechanism and predicting the origin of the chemo‐ and stereo‐selectivities on the phosphine catalyzed [2+3] and [2+4] annulations of saturated amine with allenoate. [ABSTRACT FROM AUTHOR]

The stereoselective Rauhut-Currier (RC) reaction catalyzed by a cysteine derivative has been explored computationally with density functional theory (M06-2X). Both methanethiol and a chiral cysteine derivative were studied as nucleophiles. The complete reaction pathway involves rate-determining elimination of the thiol catalyst from the Michael addition product. The stereoselective Rauhut-Currier reaction, catalyzed by a cysteine derivative as a nucleophile, has also been studied in detail. This reaction was experimentally found to be extremely sensitive to the reaction conditions, such as the number of water equivalents and the effect of potassium counterion. The E1cB process for catalyst elimination has been explored computationally for the eight possible stereoisomers. The effect of explicit water solvation and the presence of counterion (either K(+) or Na(+) ) has been studied for the lowest energy enantiomer pair (1S, 2R, 3S)/(1R, 2S, 3R).

Biocatalysis has found numerous applications in various fields as an alternative to chemical catalysis. The use of enzymes in organic synthesis, especially to make chiral compounds for pharmaceuticals as well for the flavors and fragrance industry, are the most prominent examples. In addition, biocatalysts are used on a large scale to make specialty and even bulk chemicals. This review intends to give illustrative examples in this field with a special focus on scalable chemical production using enzymes. It also discusses the opportunities and limitations of enzymatic syntheses using distinct examples and provides an outlook on emerging enzyme classes. [ABSTRACT FROM AUTHOR]

An efficient access to chiral pyrrolidine derivatives bearing one trifluoromethylated quaternary stereogenic centers is developed through Cu(I)/(S)‐TF‐BiphamPhos‐catalyzed asymmetric 1,3‐dipolar cycloaddition of azomethine ylides with tert‐butyl 2‐(trifluoromethyl)acrylate in moderate to high yields, excellent diastereoselectivities and good enantioselectivities (up to 95% yield, >20 : 1 dr, 89% ee). [ABSTRACT FROM AUTHOR]

Stereoselective alkyne semihydrogenations are attractive approaches to alkenes, which are key building blocks for synthesis. With regards to the most atom‐economic reducing agent dihydrogen (H2), only few catalysts for the challenging E‐selective alkyne semihydrogenation have been disclosed, each with a unique substrate scope profile. Here, we show that a commercially available nickel catalyst facilitates the E‐selective alkyne semihydrogenation of a wide variety of substituted internal alkynes. This results in a simple and broadly applicable overall protocol to stereoselectively access E‐alkenes employing H2, which could serve as a general method for synthesis. [ABSTRACT FROM AUTHOR]

Following the recent discovery that traditional silver(I) oxide‐promoted glycosidations of glycosyl bromides (Koenigs–Knorr reaction) can be greatly accelerated in the presence of catalytic TMSOTf, reported herein is a dedicated study of all major aspects of this reaction. A thorough investigation of numerous silver salts and careful refinement of the reaction conditions led to an improved mechanistic understanding. This, in turn, led to a significant reduction in the amount of silver salt required for these glycosylations. The progress of this reaction can be monitored by naked eye, and the completion of the reaction can be judged by the disappearance of characteristic dark color of Ag2O. Further evidence on higher reactivity of benzoylated α‐bromides in comparison to that of their benzylated counterparts has been acquired. [ABSTRACT FROM AUTHOR]

The first ortho‐alkenylation of aromatic amidines with alkynes was realized by earth‐abundant manganese catalysis through C−H activation. A catalytic amount of PhMgBr was found essential for improved efficiency of this transformation. Wide tolerance of functional groups and excellent E/Z selectivity highlighted the current protocol. [ABSTRACT FROM AUTHOR]

History of the development and use of homogeneous metal complex catalysts in the chemistry of acetylene and its derivatives is considered. Achievements of the catalytic chemistry of alkynes in the creation of affective catalytic systems (based on Groups 3—11 and 13 of the Periodic Table) for alkyne dimerization, capable of producing desired dimeric isomers possessing high chemo-, stereo- and regioselectivity are analyzed. The nature of elementary stages in four mechanisms of dimerization and the relations of the nature of organometallic intermediates to the nature of catalyst (metal and ligand), substrate, and type of mechanism, and, hence, to the selectivity of dimerization process are discussed. [ABSTRACT FROM AUTHOR]

Catalytic cycloisomerization‐initiated cascade cyclizations of terminal alkynes have received tremendous interest, and been widely used in the facile synthesis of a diverse array of valuable complex heterocycles. However, these tandem reactions have been mostly limited to noble‐metal catalysis, and are initiated by an exo‐cyclization pathway. Reported herein is an unprecedented copper‐catalyzed endo‐cyclization‐initiated tandem reaction of indolyl homopropargyl amides, where copper catalyzes both the hydroamination and Friedel–Crafts alkylation process. This method allows the practical and atom‐economical synthesis of valuable bridged aza‐[n.2.1] skeletons (n=3–6) with wide substrate scope, and excellent diastereoselectivity and enantioselectivity by a chirality‐transfer strategy. Moreover, the mechanistic rationale for this novel cascade cyclization is also strongly supported by control experiments, and is distinctively different from the related gold catalysis. [ABSTRACT FROM AUTHOR]

• Screening method was performed to select strains for the preparation of Lamivudine chiral intermediate. • A strain identified as Klebsiella oxytoca demonstrated high stereoselectivity towards (S)-enantiomer of the substrate. • The strain confers us to obtain chiral intermediate in an enzymatic way. We report the asymmetric catalysis mediated by a newly isolated strain from soil, Klebsiella oxytoca , for the preparation of the chiral intermediate of antiviral agent lamivudine which is proven to be one of most potent medicines for the treatment of human chronic hepatitis B and HIV infection. To improve the efficiency of the transformation, firstly the carbon and nitrogen sources of the medium were screened and the best performance was achieved with glucose (5 g/L) as carbon source and tryptone (5 g/L) as nitrogen source. Secondly, optimization of the reaction condition was carried out. A series of parameters were investigated including temperature, pH, metal ions, surfactant, and substrate concentration. The best outcome [enantiomeric excess (ee) of 99.9% and yield of 24%] of the enantioselective resolution of the racemic substrate catalyzed by whole cell of Klebsiella oxytoca was reached at 30 ℃, pH 7.0, substrate concentration of 1.5 g/L, and no additives. As a comparation to most of the lipase-catalyzed systems for the production of chiral oxathiolane moiety of lamivudine, the reaction occurred in a single-phase aqueous system which meets the golden and stringent criteria of green chemistry. To our knowledge, this is the first study using Klebsiella oxytoca as catalyst for the preparation of the chiral moiety of lamivudine. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synergetic effect of Lewis acid and Ru(II) catalyst was demonstrated in catalytic isomerization. • Z-isomers were found as the dominant product. • The catalytic activity improvement is Lewis acidity strength dependent. • Five-membered Ru complex from anchimeric assistance from substrate and Lewis acid was recognized as the key intermediate. In catalytic double bond migration reaction, E -configuration olefins were normally generated as the dominant product because E -configuration was thermodynamically favored. However, Z-configuration products are sometimes desired in pharmaceutical chemistry owing to the structure-activity relationship. In this paper, we have demonstrated a new strategy that Lewis acid promoted an widely employed and convenient ruthenium(II) complex for the catalytic isomerization of O-allylethers, leading to thermodynamic-unfavored Z-product under mild conditions. The model substrate of allyl phenyl ether can be simply scaled up to 20 mmol to produce Z-product with TON of 2453 and TOF of 13,430 h−1 at 40–60 °C. The system of Ru(II)/Lewis Acid catalysts was suitable for various substituted O -allylethers and other types of substrates. Through mechanism study including kinetic study, ligand inhibition effect and molecular spectroscopy, the dissociation of PPh 3 ligand by the addition of Lewis acid, and the formation a five-membered Ru complex from anchimeric assistance were both recognized as essential steps to improve the reactivity and to control the stereoselectivity of catalytic double bond migration reaction through metal hydride addition-elimination mechanism. This new strategy may provide a new opportunity to produce thermodynamic-unfavored product in heterocyclic compounds for pharmaceutical chemistry. [ABSTRACT FROM AUTHOR]

A significant number of isolable silylenes are currently known. They have quickly developed from laboratory curiosities to useful ligands in metal‐mediated homogeneous catalysis. This includes their utilization in various catalytic transformations, such as C−C cross‐coupling, cyclotrimerization, hydroformylation, borylation, deuteration, hydrosilylation, amination, hydrogenation, and transfer semi‐hydrogenation reactions. Recent studies suggest that the silylene ligands surpass the steering properties of their phosphine and N‐heterocyclic carbene (NHC) analogues and provide excellent chemo‐, regio‐, and stereoselectivites. Mechanistic studies suggest that their promoted performance of metal‐mediated catalytic transformations results from a strong σ‐donor character along with cooperative effects of their SiII centers. This Minireview covers the most recent advances in the field. No longer laboratory curiosities: Stable silylenes are a versatile family of powerful steering ligands that increase catalytic activity and selectivity. This Minireview covers the recent progress of silylene ligands in homogeneous catalysis. [ABSTRACT FROM AUTHOR]

Abstract Transition metal catalysis has enabled the highly stereoselective and protecting group-free synthesis of the C14 C23 fragment of the apoptosis-inducing natural products biselyngbyolide A and B. A Pd-catalyzed Stille reaction between a vinyl stannane and a crotyl carbonate formed the skipped diene with complete control of the trisubstituted bond and excellent control over the branched/linear products. A Cu-catalyzed Stahl oxidation was used to form the requisite aldehyde needed for a Ag-catalyzed asymmetric allylation. The latter provided the final fragment with excellent stereochemical control. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Flow chemistry and heterogenous catalysis hold incredible potential from a sustainability point of view and from a green perspective. In fact, if heterogenous catalysts are required by the chemical industry for their efficiency, on the other hand, heterogenous flow catalysis would allow performing greener and more efficient chemistry at an industrial level. In the context of sustainable flow chemistry, in this chapter we report and discuss selected examples recently published in the specialized literature on the use of supported organic and organometallic catalysts for continuous flow synthesis. The use in chemo- and stereoselective synthesis, as well as versatility and robustness of the newly developed supported catalysts are discussed. [ABSTRACT FROM AUTHOR]

• A catalytic system based on cationic gallium phthalocyanines has been developed. • SbF 6 – and Sb 2 F 11 –/Sb 3 F 16 – were used as weakly coordinating counter-anions. • This catalytic system was used for donor-acceptor cyclopropanes chemistry. • [3 + 2]-Cycloaddition/annulation reactions with aldehydes have been studied. Cationic gallium phthalocyanine (RPcGa+) catalysts with SbF 6 – and Sb 2 F 11 –/Sb 3 F 16 – weakly coordinating anions were developed and used in the catalytic chemistry of donor-acceptor (D–A) cyclopropanes and related substrates. For the first time, these processes were implemented on the examples of [3 + 2]-cycloaddition/annulation reactions of D–A cyclopropanes and styrylmalonates with various aldehydes, as well as some other transformations with different substrates. [Display omitted] [ABSTRACT FROM AUTHOR]

• Carbonyl reductase CmCR was used to produce 3-hydroxytetrahydrofuran without cofactor addition. • Two mutants MuS and MuR were designed to convert 3-TF into (S) and (R)−3HTF respectively. • The substrate loading and productivity of MuS and MuR had exceeded the ever-highest record. • (S) and (R)−3HTF were prepared, purified and characterized. Tetrahydrofuran-3-one (3TF) was regarded as a difficult-to-reduce ketone for carbonyl reductases due to its high stereosymmetry, result of which, the biosynthesis of chiral 3-hydroxytetrahydrofuran (3HTF), a key precursor of pharmaceuticals for treatment of HIV or diabetes, has been limited. Present study mined a robust carbonyl reductase CmCR from Candida metapsilosis with high activity towards 3TF using isopropanol as co-substrate (500 mM, 22 g/L/h space-time yield, 67% ee). Based on the orientation of substrate's etheryl oxygen in the substrate binding pocket, CmCR was rationally designed and two mutants MuR and MuS were screened out to completely reduce 3TF into (R)-HTF and (S)-HTF respectively with the highest 3TF loading and productivity (200 mM, 4.4 g/L/h space-time yield, 99% ee for MuR while 500 mM, 11 g/L/h space-time yield, 99% ee for MuS). The structural mechanism for the enhanced stereoselectivity was revealed that the mutagenesis changed the electrostatic potential surrounding the substrate entrance and promoted 3TF to approach, bind and form prereaction state with MuR or MuS in one certain direction, by which 3TF was converted into 3HTF with excellent optical purity. The success in this study provides a viable approach for rational design of carbonyl reductases with high enantioselectivity towards target substrates of high symmetry. [Display omitted] [ABSTRACT FROM AUTHOR]