Practical Organic Synthesis Research Articles

Challenges and perspectives in using unspecific peroxygenases for organic synthesis

In the past 20 years, unspecific peroxygenases (UPOs) have emerged as promising biocatalysts for various organic transformations. Particularly, we have witnessed great attention being paid to the screening of new enzymes and expansion of the substrates/products. However, challenges such as enzyme stability, low turnover numbers, and substrate specificity hinder their widespread utilization in practical organic synthesis. This review article provides a concrete and mini-overview of the challenges associated with using UPOs in organic synthesis and discusses strategies for enzyme engineering to overcome these limitations. The article highlights recent advancements in UPO research and presents potential solutions to enhance their catalytic efficiency, stability, substrate specificity, and regioselectivity. Additionally, the review outlines the current methodologies employed for directed evolution and protein engineering of UPOs, along with computational modeling approaches for rational enzyme design. By addressing the challenges and exploring avenues for enzyme engineering, this review aims to shed light on the prospects of UPOs in organic synthesis.

Cleavage and Noncleavage Chemistry in Reactive Oxygen Species (ROS)-Responsive Materials for Smart Drug Delivery.

The design and development of advanced drug delivery systems targeting reactive oxygen species (ROS) have gained significant interest in recent years for treating various diseases, including cancer, psychiatric diseases, cardiovascular diseases, neurological diseases, metabolic diseases, and chronic inflammations. Integrating specific chemical bonds capable of effectively responding to ROS and triggering drug release into the delivery system is crucial. In this Review, we discuss commonly used conjugation linkers (chemical bonds) and categorize them into two groups: cleavable linkers and noncleavable linkers. Our goal is to clarify their unique drug release mechanisms from a chemical perspective and provide practical organic synthesis approaches for their efficient production. We showcase numerous significant examples to demonstrate their synthesis routes and diverse applications. Ultimately, we strive to present a comprehensive overview of cleavage and noncleavage chemistry, offering insights into the development of smart drug delivery systems that respond to ROS.

Direct C(sp)-H/Si-H Cross-Coupling via Copper Salts Photocatalysis.

Reported herein is the first example of C(sp)-H/Si-H cross-coupling by photocatalysis. In terms of cheap and readily available starting materials, a series of alkynylsilanes are prepared in good to excellent yields upon visible-light irradiation of CuCl and alkynes with silane. The large scale reaction with flow chemistry and late-stage functionalization of natural products shows the potential of the transformation in practical organic synthesis of the alkynylsilanes intermediates.

Teaching an Undergraduate Organic Chemistry Laboratory Course with a Tailored Problem-Based Learning Approach

This article presents the structure of the organic chemistry laboratory Course “Synthesis and Extraction of Drugs” that is included in Modena University (Italy) in the third year of the five-year “Chemistry and Pharmaceutical Technologies” degree program. This course is unique in its kind, and it aims to provide students with the critical-thinking skills required to face practical organic synthesis. Because the “problem-based learning” approach ensures a high level of learning, we modified this approach to reconcile the students’ knowledge, the resources available compared with the number of students, and the purpose of a deep learning. Accordingly, tailored academic materials have been prepared (a textbook, a laboratory notebook, and a selection of primary literature), appropriate in-class and laboratory activities have been set up, and a grading pattern that promotes the active learning process has been defined. Although the number of students is high, following this approach, very positive results with...

ChemInform Abstract: Developments in Synthetic Application of Selenium(IV) Oxide and Organoselenium Compounds as Oxygen Donors and Oxygen‐Transfer Agents

AbstractReview: 192 refs.

Developments in Synthetic Application of Selenium(IV) Oxide and Organoselenium Compounds as Oxygen Donors and Oxygen-Transfer Agents.

A variety of selenium compounds were proven to be useful reagents and catalysts for organic synthesis over the past several decades. The most interesting aspect, which emerged in recent years, concerns application of hydroperoxide/selenium(IV) oxide and hydroperoxide/organoselenium catalyst systems, as “green reagents” for the oxidation of different organic functional groups. The topic of oxidations catalyzed by organoselenium derivatives has rapidly expanded in the last fifteen years This paper is devoted to the synthetic applications of the oxidation reactions mediated by selenium compounds such as selenium(IV) oxide, areneseleninic acids, their anhydrides, selenides, diselenides, benzisoselenazol-3(2H)-ones and other less often used other organoselenium compounds. All these compounds have been successfully applied for various oxidations useful in practical organic syntheses such as epoxidation, 1,2-dihydroxylation, and α-oxyfunctionalization of alkenes, as well as for ring contraction of cycloalkanones, conversion of halomethyl, hydroxymethyl or active methylene groups into formyl groups, oxidation of carbonyl compounds into carboxylic acids and/or lactones, sulfides into sulfoxides, and secondary amines into nitrones and regeneration of parent carbonyl compounds from their azomethine derivatives. Other reactions such as dehydrogenation and aromatization, active carbon-carbon bond cleavage, oxidative amidation, bromolactonization and oxidation of bromide for subsequent reactions with alkenes are also successfully mediated by selenium (IV) oxide or organoselenium compounds. The oxidation mechanisms of ionic or free radical character depending on the substrate and oxidant are discussed. Coverage of the literature up to early 2015 is provided. Links have been made to reviews that summarize earlier literature and to the methods of preparation of organoselenium reagents and catalysts.

Organometallic Carbanions in Practical Organic Synthesis: Grignards, Organolithiums, and More

ADVERTISEMENT RETURN TO ISSUEPREVEditorialNEXTOrganometallic Carbanions in Practical Organic Synthesis: Grignards, Organolithiums, and MoreAman A. Desai and Victor SnieckusView Author Information Aether Industries Limited, Surat 394230, Gujarat, India. E-mail: [email protected] Department of Chemistry, Queen’s University, Kingston, Ontario K7L 3N6, Canada. E-mail: [email protected]Cite this: Org. Process Res. Dev. 2014, 18, 10, 1191Publication Date (Web):October 17, 2014Publication History Published online17 October 2014Published inissue 17 October 2014https://doi.org/10.1021/op500283pCopyright © 2014 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1099Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (113 KB) Get e-AlertsSUBJECTS:Industrial manufacturing,Ketones,Organic synthesis,Organometallic reactions Get e-Alerts

ChemInform Abstract: Tandem Oxidative Processes Catalyzed by Polymer‐Incarcerated Multimetallic Nanoclusters with Molecular Oxygen

AbstractReview: 40 refs.

ChemInform Abstract: Organorhodium‐Functionalized Periodic Mesoporous Organosilica: High Hydrophobicity Promotes Asymmetric Transfer Hydrogenation in Aqueous Medium.

Three organosilica-bridged periodic mesoporous organosilicas were prepared by the immobilization of a chiral N-sulfonylated diamine-based organorhodium complex within their silicate network. Structural analysis and characterization confirmed their well-defined single-site active rhodium centers, whilst electron microscopy revealed their highly ordered hexagonal mesostructures. Among these three different organosilica-bridged periodic mesoporous organosilicas, the ethylene-bridged periodic mesoporous organosilica catalyst exhibited excellent heterogeneous catalytic activity and high enantioselectivity in the aqueous asymmetric transfer hydrogenation of aromatic ketones. This superior catalytic performance was attributed to its salient hydrophobicity, whilst its comparable enantioselectivity relative to the homogeneous catalyst was derived from the confined nature of the chiral organorhodium catalytic sites. Furthermore, this ethylene-bridged periodic mesoporous organosilica could be conveniently recovered and reused at least 12 times without the loss of its catalytic activity. This feature makes this catalyst attractive for practical organic synthesis in an environmentally friendly manner. This study offers a general way of optimizing the bridged organosilica moiety in periodic mesoporous organosilicas, thereby enhancing its catalytic activity in heterogeneous catalysis.

Tandem Oxidative Processes Catalyzed by Polymer-Incarcerated Multimetallic Nanoclusters with Molecular Oxygen

Heterogeneous catalysis and one-pot tandem reactions are key for efficient and practical organic syntheses and for green and sustainable chemistry. Heterogeneous catalysts can be recovered and reused. These catalysts can be applied to efficient systems, such as continuous-flow systems. Tandem reactions often proceed via highly reactive but unstable intermediates. Tandem reactions do not require workup or much purification of the intermediate. This Account summarizes recent developments that we have made in the field of multifunctional heterogeneous metal nanocluster catalysts for use in tandem reactions based on aerobic oxidation reactions as key processes. We constructed our heterogeneous metal nanoclusters via two important procedures--microencapsulation and cross-linking--using polystyrene-based copolymers with cross-linking moieties. These frameworks can efficiently stabilize small metal nanoclusters to maintain high catalytic activity without aggregation and leaching of nanoclusters. Aggregation and leaching are prevented by weak but multiple interactions between metal nanocluster surfaces and benzene rings in the copolymer as well as by the physical envelopment of cross-linked polymer backbones. Small nanoclusters, including multimetallic alloy clusters (nanoalloys), can be "imprisoned" into these cross-linked polymer composites. The term we use for these processes is polymer incarceration. Direct oxidative esterifications were achieved with polymer-incarcerated (PI) Au nanocluster catalysts. Amides were synthesized from alcohols and amines under aerobic oxidative conditions with PI bimetallic nanocluster catalysts composed of Au and Fe-group metals that formed separated nanoclusters rather than alloys. Oxidative lactam formation from amino alcohols was also achieved. On the other hand, imines could be prepared selectively from alcohols and amines with PI Au-Pd bimetallic nanoclusters. We also achieved the integration of the aerobic oxidation of allylic alcohols and the following Michael reaction catalyzed by trimetallic PI catalysts containing Au-Pd alloy nanoclusters and tetraalkoxyborates as cross-linkers. All of these heterogeneous catalysts could be recovered by simple operations and reused without significant loss of activity or any leaching of metals. We have demonstrated that the polymer incarceration method enables the simultaneous immobilization of several metals, with which we can achieve one-pot tandem oxidative processes using molecular oxygen as an oxidant within the multifunctional heterogeneous catalysts. Suitable choices of metals and bimetallic structures are crucial for the reactivity and the selection of reaction pathways.

ZnAl2O4@SiO2 nanocomposite catalyst for the acetylation of alcohols, phenols and amines with acetic anhydride under solvent-free conditions

A ZnAl2O4@SiO2 nanocomposite was prepared from metal nitrates and tetraethyl orthosilicate by the sol-gel process, and characterized by X-ray diffraction, Fourier transform infrared, transmission electron microscopy, and N2 adsorption-desorption measurements. The nanocomposite was tested as a heterogeneous catalyst for the acetylation of alcohols, phenols, and amines under solvent-free conditions. Under optimized conditions, efficient acetylation of these substrates with acetic anhydride over the ZnAl2O4@SiO2 nanocomposite was obtained. Acetylation of anilines and primary aliphatic amines proceeded rapidly at room temperature, while the reaction time was longer for the acetylation of alcohols and phenols, showing that an amine NH2 group can be selectively acetylated in the presence of alcoholic or phenolic OH groups. The catalyst can be reused without obvious loss of catalytic activity. The catalytic activity of the ZnAl2O4@SiO2 nanocomposite was higher than that of pure ZnAl2O4. The method gives high yields, and is clean, cost effective, compatible with substrates having other functional groups and it is suitable for practical organic synthesis.

Sol–gel derived LaFeO3/SiO2 nanocomposite: synthesis, characterization and its application as a new, green and recoverable heterogeneous catalyst for the efficient acetylation of amines, alcohols and phenols

LaFeO3/SiO2 nanocomposite was synthesized by the sol–gel process from metal nitrates and tetraethyl orthosilicate (TEOS) as the SiO2 source. The nanocomposite product was characterized by XRD, FT-IR, SEM, and surface area measurements and was used as a heterogeneous catalyst for the efficient acetylation of amines, alcohols and phenols to the corresponding acetates using acetic anhydride under solvent-free conditions. Among the various substrates, acetylation of amines was preceded rapidly, so that an amine group could be selectively acetylated in the presence of alcoholic or phenolic hydroxyl groups by the appropriate choice of reaction time. The catalyst can also be reused several times without the loss of activity. In addition, the catalytic activity of the LaFeO3/SiO2 nanocomposite was higher than that of the pure LaFeO3 nanoparticles. The method is high yielding, clean, cost effective, compatible with the substrates having other functional groups and very suitable for the practical organic synthesis.

Organorhodium‐Functionalized Periodic Mesoporous Organosilica: High Hydrophobicity Promotes Asymmetric Transfer Hydrogenation in Aqueous Medium

Three organosilica-bridged periodic mesoporous organosilicas were prepared by the immobilization of a chiral N-sulfonylated diamine-based organorhodium complex within their silicate network. Structural analysis and characterization confirmed their well-defined single-site active rhodium centers, whilst electron microscopy revealed their highly ordered hexagonal mesostructures. Among these three different organosilica-bridged periodic mesoporous organosilicas, the ethylene-bridged periodic mesoporous organosilica catalyst exhibited excellent heterogeneous catalytic activity and high enantioselectivity in the aqueous asymmetric transfer hydrogenation of aromatic ketones. This superior catalytic performance was attributed to its salient hydrophobicity, whilst its comparable enantioselectivity relative to the homogeneous catalyst was derived from the confined nature of the chiral organorhodium catalytic sites. Furthermore, this ethylene-bridged periodic mesoporous organosilica could be conveniently recovered and reused at least 12 times without the loss of its catalytic activity. This feature makes this catalyst attractive for practical organic synthesis in an environmentally friendly manner. This study offers a general way of optimizing the bridged organosilica moiety in periodic mesoporous organosilicas, thereby enhancing its catalytic activity in heterogeneous catalysis.

Cooperative Asymmetric Catalysis Using Thioamides toward Truly Practical Organic Syntheses

AbstractAsymmetric catalysis has established its unwavering position in organic chemistry as a particularly efficient strategy for the production of enantiomerically enriched compounds. For a truly practical synthetic protocol, however, asymmetric catalysis must be endowed with high atom economy and sustainability. Cooperative activation is a powerful strategy to drive efficient asymmetric catalysis without the use of stoichiometric activating reagents, leading to asymmetric catalysis with minimum waste production. This review summarizes the utility of thioamides as an emerging functional group class in cooperative asymmetric catalysis. Soft Lewis acid/hard Brønsted base cooperative catalysts, in which thioamides serve as either electrophiles or pronucleophiles, promote asymmetric CC bond‐forming reactions with perfect atom economy.

Practical iron-catalyzed atom/group transfer and insertion reactions

Iron-catalyzed reactions are receiving a surge of interest owing to the natural abundance and biocompatibility of Fe and the urge to develop practically useful sustainable catalysis for fine chemical industries. This article is a brief account of our studies on the C–O and C–N bond formation reactions catalyzed by Fe complexes supported by oligopyridine, macrocyclic tetraaza, and fluorinated porphyrin ligands. The working principle is the in situ generation of reactive Fe=O and Fe=NR intermediates supported by these oxidatively robust N-donor ligands for oxygen atom/nitrogen group transfer and insertion reactions. The catalytic reactions include C–H bond oxidation of saturated hydrocarbons (up to 87 % yield), epoxidation of alkenes (up to 96 % yield), cis-dihydroxylation of alkenes (up to 99 % yield), epoxidation–isomerization (E–I) reaction of aryl alkenes (up to 94 % yield), amination of C–H bonds (up to 95 % yield), aziridination of alkenes (up to 95 % yield), sulfimidation of sulfides (up to 96 % yield), and amide formation from aldehydes (up to 89 % yield). Many of these catalytic reactions feature high regio- and diastereoselectivity and/or high product yields and substrate conversions, and recyclability of the catalyst, demonstrating the applicability of Fe-catalyzed oxidative organic transformation reactions in practical organic synthesis.

ChemInform Abstract: Asymmetric Cu(II) Catalyses for Cycloaddition Reactions Based on π‐Cation or n‐Cation Interactions

AbstractReview: 62 refs.

Asymmetric Cu(ii) catalyses for cycloaddition reactions based on π–cation or n–cation interactions

The rational design of small but highly functional artificial catalysts is very important for practical organic synthesis. Asymmetric Lewis acid catalyses with non-covalent secondary interactions have been developed for enantioselective reactions. This tutorial review describes the concept, design and examples of asymmetric Cu(ii) catalyses for cycloaddition reactions based on intramolecular π-cation or n-cation interactions between the copper(ii) cation and auxiliary Lewis basic sites of the chiral ligands.

Spinel-type zinc aluminate (ZnAl 2O 4) nanoparticles prepared by the co-precipitation method: A novel, green and recyclable heterogeneous catalyst for the acetylation of amines, alcohols and phenols under solvent-free conditions

Zinc aluminate (ZnAl 2O 4) nanoparticles with an average particle size of about 8 nm were easily prepared by the co-precipitation method using aqueous ammonia solution as the precipitating agent. This nanosized spinel-type oxide was characterized by TGA, XRD, FT-IR, TEM, and surface area measurement and used as the heterogeneous catalyst for the acetylation reaction. Efficient acetylation of various amines, alcohols and phenols was carried out over ZnAl 2O 4 nanoparticles using acetic anhydride and/or acetyl chloride as the acetylating agents at room temperature without the use of a solvent. The method is highly selective, allowing the alcoholic hydroxyl group to be protected while the phenolic hydroxyl group remains intact, and the amine group can be acetylated in the presence of the hydroxyl group. This method is fast and has a high yield. It is also clean, safe, cost effective, compatible with substrates that have other functional groups and very suitable for practical organic synthesis. In addition, the catalyst can be reused without significant loss of activity. Indeed, the catalytic activity of the ZnAl 2O 4 nanoparticles is higher than that of bulk ZnAl 2O 4.

Organoammonium Salt-Catalyzed Enantioselective Cycloaddition Reactions with α-(Acyloxy)- or α-Diacylaminoacroleins

Abstract The rational design of small-molecule chiral catalysts is an important subject in the development of practical organic syntheses. We have designed primary ammonium salt catalysts for enantioselective cycloaddition reactions with α-substituted acroleins such as α-(acyloxy)acroleins and α-diacylaminoacroleins. Ammonium salts of an aliphatic triamine derived from H–l-Phe–l-Leu–N(CH2CH2)2 successfully promote the Diels–Alder reaction of α-(acyloxy)acroleins and α-(N,N-diacylamino)acroleins, and the [2 + 2] cycloaddition reaction of α-(acyloxy)acroleins with high enantioselectivity. An ammonium salt of a C2-symmetric aromatic diamine, 1,1′-binaphthyl-2,2′-diamine, with a superacid is also an efficient catalyst and shows high activity and enantioselectivity for the Diels–Alder reaction of cyclic dienes with α-(acyloxy)acroleins.

Bismuth ferrite (BiFeO 3) nanopowder prepared by sucrose-assisted combustion method: A novel and reusable heterogeneous catalyst for acetylation of amines, alcohols and phenols under solvent-free conditions

Bismuth ferrite (BiFeO 3) nanopowder was prepared by the novel combustion technique using sucrose as a fuel. The catalyst was characterized by using XRD, FT-IR, scanning electron microscope (SEM), transmission electron microscope (TEM), and BET surface area measurement and used as the heterogeneous catalyst for the acetylation reaction under solvent-free conditions. Efficient and selective acetylation of various amines, alcohols and phenols was carried out over BiFeO 3 nanopowder by using acetic anhydride and/or acetyl chloride as the acetylating agents at room temperature under solvent-free conditions. The method is highly chemoselective – alcoholic hydroxyl group can be protected while phenolic hydroxyl group remains intact and the amine group can be acetylated in the presence of hydroxyl. This method is fast, high yielding, clean, safe, cost effective, compatible with the substrates having other functional groups and very suitable for practical organic synthesis. The catalyst can also be reused for acetylation without loss of catalytic activity.