Showing papers in "Green synthesis and catalysis in 2023"
TL;DR: In this article , a waste-minimized continuous flow process for the synthesis of 1,4-disubstituted β-keto 1,2,3-triazoles exploiting the use of a copper tube flow reactor (CTFR).
Abstract: Metal contamination is a waste-generating and serious issue in the synthesis of chemicals, in particular in the case of products with biological activity. The appropriate selection of operating conditions plays a crucial role in the abatement of metal leaching in solution and associated wastes. Herein we report a waste-minimized continuous flow process for the synthesis of 1,4-disubstituted β-keto 1,2,3-triazoles exploiting the use of a copper tube flow reactor (CTFR). The selection of the proper azeotropic mixture allowed an almost quantitative recovery of the reaction medium greatly influencing the E-factor of the protocol. A thorough understanding of the main parameters affecting the waste generation was given by calculation of the E-factor distribution for different work-up tested under batch and flow conditions. Furthermore, the measurement of different green metrics (AE: Atom Economy, SF: Stoichiometric Factor, RME: Reaction Mass Efficiency, and MRP: Mass Recover Parameter) clearly demonstrated the benefits of the flow scale-up that allowed to perform a low environmental footprint CuAAC reaction.
2 citations
TL;DR: In this paper , the authors summarized the developments and advancements of allyl-(aza)allyl coupling reactions in the past years and organized them according to the transition metals used in allyl-allyl couplings including their own work.
Abstract: We have summarized the developments and advancements of allyl-(aza)allyl coupling reactions in the past years. Since the first report in 1980, Pd-catalyzed allyl-allyl couplings have not drawn chemists' much attention for almost 20 years. Not until the last two decades, transition-metal-catalyzed allyl-(aza)allyl transformations have been retrieved vital interest and significantly developed in many respects, including metal-catalyst, ligand development, mechanistic understanding, substrate scope, and applications in the preparation of complex functional molecules. This review is organized according to the transition metals used in allyl-allyl coupling reactions including our own work. Besides, transition-metal-free, allyl-azaallyl cross-couplings and applications in the total synthesis of natural products and drugs have also been included.
2 citations
TL;DR: In this paper , a metal and oxidant-free alkenyl C-H thiolation enabled by the azo group was established for the modular synthesis of tetrasubstituted acyclic olefins.
Abstract: Metal- and oxidant-free alkenyl C–H thiolation enabled by the azo group had been established for the modular synthesis of tetrasubstituted acyclic olefins. The reaction was performed under mild reaction conditions with a broad substrate scope. The intramolecular 6-membered hydrogen-bonding network accounts for the observed excellent stereo-control.
2 citations
TL;DR: In this article , the consecutively paired electrolytic-mediated controllable radical cross-coupling of thiophenols with dichloromethane was developed to deliver the dithioacetals, sulfides, and sulfoxides in the absence of electrochemical mediator conditions.
Abstract: Chloroalkanes are important building blocks in the synthesis, but their use in redox chemistry is limited by their negative reduction potentials. Electrosynthesis can precisely control the reaction energy just by adjusting the current or voltage to achieve the selectivity of regulation. In this study, the consecutively paired electrolytic-mediated controllable radical cross-coupling of thiophenols with dichloromethane was developed to deliver the dithioacetals, sulfides, and sulfoxides in the absence of electrochemical mediator conditions. It features broad substrate scope, simple operation, gram-scale synthesis, and is eco-friendly. Mechanistic studies reveal that this electrochemical reaction is radical-induced cross-coupling of thiophenols with dichloromethane.
1 citations
TL;DR: In this paper , the authors described the selected recent examples of how developed intermolecular C(sp2)-H functionalization methodologies involving diverse techniques diversify pharmaceutical molecules in the late stage.
Abstract: C–H late-stage functionalization has gradually become a powerful approach for the rapid optimization of lead compounds’ bioactivity. Significant advances in this field have been achieved in the past few years, mainly, the C–H functionalization system in (hetero)aryl C–H activation owing to the importance of (hetero)aryl moiety in pharmaceutical. In this review, we described the selected recent examples of how developed intermolecular C(sp2)–H functionalization methodologies involving diverse techniques diversify pharmaceutical molecules in the late stage.
1 citations
1 citations
TL;DR: In this paper , a defluorinative ring-opening of gem-difluorocyclopropenes is presented, providing a concise and efficient method for accessing 2-fluoropropenals and 2fluorobuta-1,3-dienes in moderate to good yields with excellent regio-and stereoselectivities.
Abstract: A novel defluorinative ring-opening of gem-difluorocyclopropenes is presented, providing a concise and efficient method for accessing 2-fluoropropenals and 2-fluorobuta-1,3-dienes in moderate to good yields with excellent regio- and stereoselectivities. The reaction is performed under mild conditions with no need of using an excess amount of nucleophilic reagents. Water plays a crucial role in this transformation.
1 citations
TL;DR: Transition-metal-catalyzed C-H bond functionalization has attracted tremendous attention as an increasingly important protocol for the construction of C-C and C-X bonds as mentioned in this paper .
Abstract: Transition-metal-catalyzed C–H bond functionalization has attracted tremendous attention as an increasingly important protocol for the construction of C–C and C–X bonds. In particular, C–H bond functionalization assisted by the phosphorus-containing directing groups has made significant progress in the past few years. A series of valuable phosphorous compounds, especially phosphine ligands have been provided conveniently. This review comprehensively describes recent advances in transition-metal-catalyzed C–H bond functionalization assisted by the phosphorus-containing directing groups, highlights its potential applications in organic synthesis, and gives some insights into future advances.
1 citations
TL;DR: In this article , a dehydroxylative ring-opening Giese reaction of cyclobutanone oximes enabled by photoredox/Ti dual catalysis has been reported, which avoids the prefunctionalization of oximes and the use of stoichiometric triarylphosphine reagents.
Abstract: A dehydroxylative ring-opening Giese reaction of cyclobutanone oximes enabled by photoredox/Ti dual catalysis has been reported in this work. This protocol avoids the prefunctionalization of oximes and the use of stoichiometric triarylphosphine reagents. It also features mild conditions, broad substrate scope and good functional group tolerance. The gram-scale reaction, product derivatization, late-stage functionalization of complex pharmaceutical and natural product derivatives, and oligopeptide modification exhibit the potential application of this methodology in synthetic chemistry.
TL;DR: In this paper , a novel zwitterionic polymer (PDDC) with a cellular structure via self-complexation of copolymer bearing both quaternary ammonium cation and carboxylate anion was employed as a recyclable catalyst for N-methylation of atmospheric CO2 and various amines with hydrosilane as a reductant, affording more than 17 nethylamines in good to excellent yields (up to 99%) under mild conditions.
Abstract: Using heterogeneous catalysts to promote the construction of the C–N bond between amines and CO2 under mild conditions is a challenge yet. Herein, we synthesized a novel zwitterionic polymer (PDDC) with a cellular structure via self-complexation of copolymer bearing both quaternary ammonium cation and carboxylate anion. PDDC was employed as a recyclable catalyst for N-methylation of atmospheric CO2 and various amines with hydrosilane as a reductant, affording more than 17 N-methylamines in good to excellent yields (up to 99%) under mild conditions. The behavior of PDDC in the reaction medium was disclosed by using a dynamic light scattering study, revealing that the decreased hydraulic radius of particle size contributes to exposing more active sites and increasing reaction activity. Utilizing a series of designed experiments and density functional theory calculations uncovered the crucial role of the prepared zwitterionic polymer during the reaction procedure of CO2 conversion.
TL;DR: In this paper , a distal heteroaryl migration process was used to synthesize a variety of valuable alkylsulfonyl-substituted compounds, which were then used for unactivated alkenes to undergo efficient intermolecular reactions.
Abstract: Photocatalyzed alkylsulfonylation of unactivated alkenes using DABCO. (SO2)2 and thianthrenium salts via a distal heteroaryl migration process has been developed, which provides a new means of synthesizing a variety of valuable alkylsulfonyl-substituted compounds. These alkylsulfonyl radicals couple with unactivated alkenes to undergo efficient intermolecular reactions, followed by distal heteroaryl migration. This mild catalytic method is tolerant of functional groups and affords medicinally relevant alkylsulfonylated heterocycles.
TL;DR: In this article , the authors outlined recent trends and developments of catalytic enantioselective systems for the generation of enantioenriched profens and their derivatives, and divided these transformations into three categories: transition metal-catalyzed asymmetric cross-couplings and organocatalytic asymmetric transformations.
Abstract: The profens belong to a class of nonsteroidal anti-inflammatory drugs (NSAIDs), which exert significant anti-inflammatory, analgesic, antipyretic and other pharmacological effects. A considerable number of catalytic asymmetric strategies for the synthesis of enantioenriched profens have been introduced. Herein are outlined recent trends and developments of promising catalytic enantioselective systems for the generation of profens and their derivatives. According to the reaction type, we divided these transformations into three categories: Transition metal-catalyzed asymmetric hydrogenations, transition metal-catalyzed asymmetric cross-couplings and organocatalytic asymmetric transformations. Overviews of generic reaction mechanisms are presented. Ideally, this tutorial review will motivate further interest in the catalytic asymmetric synthesis of highly enantioenriched profens.
TL;DR: In this article , a mild and efficient photocatalytic-induced radical method was developed for cycloaddition reaction of 1,4-disubstituted 1,2,3-triazoles with N-tosylhydrazides and primary amines.
Abstract: Available online A mild and efficient photocatalytic-induced radical method has been developed for [4 + 1] cycloaddition reaction of 1,4-disubstituted 1,2,3-triazoles with N-tosylhydrazides and primary amines. The reaction is catalyzed by 20 mol% of I2 under metal, azide and oxidant-free conditions. The method is based upon the photocatalytic generation of allyl-type radicals, followed by the iodine-catalyzed production of azoalkenes, which react rapidly with various anilines.
TL;DR: In this paper , a colorimetric high-throughput screening assay was successfully developed based on a dual-enzyme cascade for the engineering of the P450DA's hydroxylation activity.
Abstract: Chiral methyl mandelates are useful synthons in organic transformation and pharmaceutical synthesis. Green synthesis of these valuable compounds by direct C–H activating oxidative hydroxylation has attracted keen interest. Described herein is achieving the stereoselective and efficient bio-hydroxylation of methyl 2-phenylacetates to the chiral methyl mandelates by directed evolution of the cytochrome P450DA hydroxylase. In the present study, a new colorimetric high-throughput screening assay was successfully developed based on a dual-enzyme cascade for the engineering of the P450DA's hydroxylation activity. Several beneficial variants with enhanced bio-hydroxylation activity were created by combining random mutagenesis and site-saturated/directed mutagenesis strategies. Whole-cell bio-hydroxylation of various methyl 2-phenylacetates using the best septuplet-mutant P450DA-11 yielded the corresponding chiral methyl mandelates in up to 92% isolated yields and >99% ee.
TL;DR: An authoritative and up-to-date discussion of enzyme engineering, methodology development and its applications can be found in this paper , where the authors present an overview of the most recent developments in enzyme engineering.
Abstract: An authoritative and up-to-date discussion of enzyme engineering, methodology development and its applications.
TL;DR: In this article , core-shell structured magnetic wrinkled organosilica-based metal-enzyme integrated catalysts were synthesized and their catalytic performances were studied in the chemoenzymatic dynamic kinetic resolution of chiral amines in an organic solvent.
Abstract: Core-shell structured magnetic wrinkled organosilica-based metal-enzyme integrated catalysts were synthesized, and their catalytic performances were studied in the chemoenzymatic dynamic kinetic resolution of chiral amines in an organic solvent, as well as in the chemoenzymatic synthesis of chiral alcohols in water. Structure-performance studies revealed the important influence of their tunable structure and composition on the optimization of activity, stability, and recyclability in chemoenzymatic catalysis.
TL;DR: In this paper , a sustainable synthesis of 3,3-disubstituted oxindoles via a Michael-type reaction based on the CuBr-catalysed capture of carboxylic oxonium ylides with isatylidene malononitrile was reported.
Abstract: We herein reported a sustainable synthesis of 3,3-disubstituted oxindoles via a Michael-type reaction based on the CuBr-catalysed capture of carboxylic oxonium ylides with isatylidene malononitrile. The reaction is characterized by a high atom economy and low economic constraints. The catalyst CuBr could be conveniently recyclized. The products of the reaction were found to be inhibitory against Na ion channels. We expect the reaction to shed the light on synthesis of biologically interesting molecules directed by principles of green chemistry.
TL;DR: In this article , an iron-catalyzed annulation of amidines with α,β-unsaturated ketoxime acetates is described, which employs amidines as CN units and provides a new protocol for the construction of 2,4,6-trisubstituted pyrimidines under batch and continuous flow conditions in moderate to good yields.
Abstract: An iron-catalyzed [4 + 2] annulation of amidines with α,β-unsaturated ketoxime acetates is described. This strategy employs amidines as CN units and provides a new protocol for the construction of 2,4,6-trisubstituted pyrimidines under batch and continuous flow conditions in moderate to good yields, exhibiting good functional group tolerance, scalability and operational simplicity.