I'm a PhD student in Chemistry who likes "cooking" compounds than food.
Development of a catalyst for environmental friendly and effective tandem reaction
Cooking pasta dishes requires us to prepare the sauce first and then add separately cooked pasta. Have you ever wished to streamline the process by throwing all the ingredients for the sauce and the raw pasta in one pot? Chemists also prefer to do the same thing when they synthesize compounds that require a sequence of multiple reactions. As a result, there is an effort to develop tandem reactions, processes in which several reactions are conducted in the same flask simultaneously. This is possible with the utilization of catalysts that allow the reactions to occur in the right order and in an efficient way. Tandem reactions not only reduce time and labor, but also eliminate waste generated in the sequential process.
To give an example, my project focuses on developing a catalyst for synthesis of epoxides, high-valued intermediates in polymer production. Normally, the synthesis is done by the oxidation of alkenes with commercially available hydrogen peroxide (H2O2). The current production of H2O2 involves purification, storage, and transportation which has major energy costs and safety concerns. To eliminate these steps, I integrated H2O2 synthesis and the alkene oxidation into a tandem reaction by mixing H2 gas, O2 gas, alkenes, and my catalyst in one pot. The catalyst allows H2 and O2 to react and produce H2O2, which will be simultaneously used to oxidize alkene to desired epoxide product.
Many syntheses of useful compounds around us have gained tremendous benefit from being carrying out in a tandem fashion. Check out this pinboard for more insight in these processes and learn about my research.
Abstract: A novel bifunctional squaramide-catalyzed vinylogous Michael-Michael cascade reaction of 3-alkylidene oxindoles with nitroolefin enoates was developed. This convenient, one-pot cascade reaction serves as a powerful tool for the enantioselective construction of potential bioactive chiral chromans, which have three continuous tertiary stereocenters, in moderate to good yields (up to 85%) with excellent stereoselectivities (up to >19:1 dr and >99% ee).
Pub.: 27 Jun '17, Pinned: 03 Jul '17
Abstract: A novel vanadium-catalyzed one pot domino reaction of 1,2-diketones with amidines has been identified that enables their transformation into imides and amides. The reaction proceeds by dual acylation of amidines via oxidative C(CO)-C(CO) bond cleavage of 1,2-diketones to afford N,N'-diaroyl-N-arylbenzamidine intermediates. In the reaction, these intermediates are easily hydrolyzed into imides and amides through vanadium catalysis. This method provides a practical, simple and mild synthetic approach to access a variety of imides as well as amides in high yields. Moreover, one step construction of imide and amide bond with long chain alkyl group is an attractive feature of this protocol.
Pub.: 28 Jun '17, Pinned: 03 Jul '17
Abstract: A practical one-pot cascade reaction protocol provides direct access to valuable 1,2,4-trisubstituted pyrroles. The process involves an N-heterocyclic carbene (NHC)-catalyzed Stetter-type hydroformylation using glycolaldehyde dimer as a novel C1 building-block, followed by a Paal-Knorr condensation with primary amines. The reaction makes use of simple and commercially available starting-materials and catalyst, an important feature regarding applicability and utility. Low catalyst loading under mild reaction conditions afforded a variety of 1,2,4-substituted pyrroles in a transition-metal free reaction with high step economy and good yields. This methodology is applied in the synthesis of a versatile Atorvastatin precursor which allows a variety of modifications at the pyrrole core structure.
Pub.: 01 Jul '17, Pinned: 03 Jul '17
Abstract: The first total synthesis of waihoensene, a tetracyclic diterpene containing an angular triquinane and a six-membered ring, with four contiguous quaternary carbon atoms, was achieved through the tandem cycloaddition reaction of an allenyl diazo substrate containing a six-membered ring via trimethylenemethane (TMM) diyl intermediate.
Pub.: 26 May '17, Pinned: 03 Jul '17
Abstract: An unprecedented coupling reaction between aromatic amines and diazo compounds was well developed, which afforded a bridge connecting between radical chemistry and metal carbene chemistry. This Mn-catalyzed tandem reaction also provided a fundamentally different and practical approach to the indole skeleton under mild conditions.
Pub.: 18 May '17, Pinned: 03 Jul '17
Abstract: We report the concise total synthesis of homodimericin A (1), a recently identified fungal metabolite bearing an unprecedented molecular architecture. The success of the approach hinges on a series of rationally designed and bioinspired transformations, including a Moore rearrangement to assemble the monomeric hydroquinone precursor, homodimerization through double Michael addition to construct the planar A/B/C tricyclic framework, and a tandem Diels–Alder reaction/carbonyl–ene cyclization to forge the congested D/E/F tricyclic cage motif. Unequivocal evidence for the elucidated structure of homodimericin A was also provided by this study.
Pub.: 16 May '17, Pinned: 03 Jul '17
Abstract: A novel in situ generated TEMPO oxoammonium salt-mediated one-pot tandem reaction has been developed for the straightforward construction of pyrrolin-4-ones from readily available β-oxoamides with amine hydrochlorides. The reaction tolerates various functional groups and represents a reliable method for the synthesis of highly substituted pyrrolin-4-ones in good yields under mild conditions. Detailed mechanistic studies disclosed that TEMPO oxoammonium salt generated in situ was crucial for the transformation involving the formation of enaminone precursors in situ by condensation of the β-oxoamides with amines, followed by sequential oxidative coupling with β-oxoamides, intramolecular cyclization, and 1, 2-alkyl migration steps.
Pub.: 19 May '17, Pinned: 03 Jul '17
Abstract: The inside back cover picture shows a one-pot tandem reaction involving in situ enzymatic synthesis of S-adenosylmethionine by using SalL, followed by C−C bond formation by using the C-methyltransferase NovO. This system is compatible with both methionine and methionine analogues as the alkyl donor. More information can be found in the communication by L. D. Humphreys, G. A. Burley et al. (DOI: 10.1002/cbic.201700115).
Pub.: 15 May '17, Pinned: 03 Jul '17
Abstract: A unique tandem reaction of sequence-controlled cationic copolymerization and site-specific hetero Diels-Alder (DA) reaction is demonstrated. In the controlled cationic copolymerization of furfural and 2-acetoxyethyl vinyl ether (AcOVE), only the furan ring adjacent to the propagating carbocation underwent the hetero DA reaction with the aldehyde moiety of another furfural molecule. A further and equally important feature of the copolymerization is that the obtained copolymers had unprecedented 2:(1+1)-type alternating structures of repeating sequences of two VE and one furfural units in the main chain and one furfural unit in the side chain. The specific DA reaction is attributed to the delocalization of the positive charge to the side furan ring.
Pub.: 02 Jun '17, Pinned: 03 Jul '17
Abstract: A palladium catalyst (Pd-Cs) encapsulated metalloporphyrin network PIZA-1 thin film with bifunctional properties has been developed through a modified epitaxial layer-by-layer encapsulation approach. Combining the oxidation activity of Pd-Cs and the acetalization activity of the Lewis acidic sites in the PIZA-1 thin film, this bifunctional catalyst of the Pd-Cs@PIZA-1 thin film exhibits a good catalytic activity in a one-pot tandem oxidation-acetalization reaction. Furthermore, the surface components can be controlled by ending the top layer with different precursors in the thin film preparation procedures. The catalytic performances of these thin films with different surface composites were studied under the same conditions, which showed different reaction conversions. The result revealed that the surface component can influence the catalytic performance of the thin films. This epitaxial encapsulation offers a good understanding of the tandem catalysis for thin film materials and provides useful guidance to develop new thin film materials with catalytic properties.
Pub.: 03 Jun '17, Pinned: 03 Jul '17
Abstract: The 'off' state for aminocatalysis by a switchable rotaxane is shown to correspond to an 'on' state for anion-binding catalysis. Conversely, the aminocatalysis 'on' state of the dual-function rotaxane is inactive in anion-binding catalysis. Switching between the different states is achieved through the stimuli-induced change of position of the macrocycle on the rotaxane thread. The anion-binding catalysis results from a pair of triazolium groups that act together to CH-hydrogen bond to halide anions when the macrocycle is located on an alternative (ammonium) binding site, stabilizing the in situ generation of benzhydril cation and oxonium ion intermediates from activated alkyl halides. The aminocatalysis and anion-binding catalysis sites of the dual-function rotaxane catalyst can be sequentially concealed or revealed, enabling catalysis of both steps of a tandem reaction process.
Pub.: 20 Jun '17, Pinned: 03 Jul '17
Abstract: An aza-Michael addition-asymmetric transfer hydrogenation tandem process for preparation of chiral γ-secondary amino alcohols has been developed. This one-pot tandem process involves an aza-Michael addition of aryl-substituted enones and amines to form aryl-substituted γ-secondary amino ketones, followed by a Ru-catalyzed asymmetric transfer hydrogenation to form aryl-substituted γ-secondary amino alcohols. An advantageous feature of this tandem reaction is that it provides various γ-secondary amino alcohols in high yields with high enantioselectivities.
Pub.: 01 Jun '17, Pinned: 30 Jun '17
Abstract: A novel Mn(II)-promoted tandem phosphorylation/cyclization reaction of 2-biaryl isothiocyanates with phosphine oxides was described. This is the first general method to synthesize 6-phosporylated phenanthridines from 2-biaryl isothiocyanates. The approach is featured by oxidant-free, low loading of P-reagent, easy operation, and high functional group tolerance.
Pub.: 14 Jun '17, Pinned: 30 Jun '17
Abstract: A versatile and highly efficient three-step, one-pot, enzyme-promoted Passerini tandem reaction has been developed. The chemoenzymatic sequence involved simultaneous enzyme catalyzed hydrolysis, subsequent Passerini reaction, and enzymatic kinetic resolution of the Passerini product. This methodology combines the diversity delivered by multicomponent reactions with the selectivity of biocatalysts, which results in efficient synthesis of the target compounds with excellent enantiomeric excesses of up to 99 %. With a small set of substrates, a large library of complex molecules was obtained within a short time by using the developed procedure.
Pub.: 20 Jun '17, Pinned: 30 Jun '17
Abstract: A metal-free, visible-light-promoted direct difunctionalization of alkynoates was achieved under mild conditions. By employing catalytic quantities of the commercially available Eosin Y (EY) as the photocatalyst and tert-butyl-hydroperoxide (TBHP) as the oxidant, we developed a radical tandem phosphorylation/cyclization reaction to synthesize various 3-phosphorylated coumarins with high functional group tolerance, moderate to good yields, and excellent regioselectivities.
Pub.: 26 Jun '17, Pinned: 30 Jun '17
Abstract: A CuI-loaded and n-pentadecyl-attached imidazolium salt decorated UiO-67-type MOF catalyst for one-pot azide−alkyne cycloaddition is reported.A CuI-loaded and n-pentadecyl-attached imidazolium salt decorated UiO-67-type metal–organic framework (CuI@UiO-67-IM, 2) based on a new premodified ligand L (n-pentadecyl-attached imidazolium (IM) decorated dicarboxylic acid) and ZrCl4 is reported. Compound 2 can be a bifunctional composite heterogeneous phase-transfer catalyst to promote the azide–alkyne cycloaddition (H2O, air, 80 °C) from corresponding halogenated compounds and sodium azide as a sequential one-pot procedure with high yields and excellent regioselectivity.
Pub.: 26 Jun '17, Pinned: 29 Jun '17
Abstract: Tandem catalytic systems, often inspired by biological systems, offer many advantages in the formation of highly functionalized small molecules. Herein, a new metal-organic framework (MOF) with porphyrinic struts and Hf6 nodes is reported. This MOF demonstrates catalytic efficacy in the tandem oxidation and functionalization of styrene utilizing molecular oxygen as a terminal oxidant. The product, a protected 1,2-aminoalcohol, is formed selectively and with high efficiency using this recyclable heterogeneous catalyst. Significantly, the unusual regioselective transformation occurs only when an Fe-decorated Hf6 node and the Fe-porphyrin strut work in concert. This report is an example of concurrent orthogonal tandem catalysis.
Pub.: 06 Oct '15, Pinned: 29 Jun '17
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