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Chemical & Pharmaceutical Bulletin 2022Knoevenagel condensation, an olefin-forming reaction from active methyl/methylene-containing compounds and aldehydes, is a fundamental and useful synthetic method....
Knoevenagel condensation, an olefin-forming reaction from active methyl/methylene-containing compounds and aldehydes, is a fundamental and useful synthetic method. Benzothiazoles are, however, out of the scope of Knoevenagel condensation. Here, we report that Knoevenagel condensation between aldehydes and 2-methyl-thiazolo[4,5-b]pyrazines (MeTPy), a fused ring structure comprising pyrazine and thiazole, proceeded smoothly, despite minor structural differences from benzothiazoles. This finding will be useful for short synthesis of MeTPy-containing functional molecules, such as a tau probe analog 1.
Topics: Aldehydes; Alkenes; Molecular Structure; Pyrazines
PubMed: 34980738
DOI: 10.1248/cpb.c21-00780 -
Molecules (Basel, Switzerland) Mar 2016Organic azides are key motifs in compounds of relevance to chemical biology, medicinal chemistry and materials science. In addition, they also serve as useful building... (Review)
Review
Organic azides are key motifs in compounds of relevance to chemical biology, medicinal chemistry and materials science. In addition, they also serve as useful building blocks due to their remarkable reactivity. Therefore, the development of efficient protocols to synthesize these compounds is of great significance. This paper reviews the major applications and development of azidation in difunctionalization of olefins using azide reagents.
Topics: Alkenes; Azides; Catalysis; Models, Chemical
PubMed: 26999085
DOI: 10.3390/molecules21030352 -
Nature Communications Jun 2018Developing physical models of complex dynamic systems showing emergent behaviour is key to informing on persistence and replication in biology, how living matter emerges...
Developing physical models of complex dynamic systems showing emergent behaviour is key to informing on persistence and replication in biology, how living matter emerges from chemistry, and how to design systems with new properties. Herein we report a fully synthetic small molecule system in which a surfactant replicator is formed from two phase-separated reactants using an alkene metathesis catalyst. The replicator self-assembles into aggregates, which catalyse their own formation, and is thermodynamically unstable. Rather than replicating until the reactants are fully consumed, the metastable replicator is depleted in a second metathesis reaction, and closed system equilibrium is eventually reached. Mechanistic experiments suggest phase separation is responsible for both replicator formation and destruction.
Topics: Alkenes; Catalysis; DNA Replication; Kinetics; Methanol; Models, Chemical; Molecular Structure; Organic Chemicals; Origin of Life; Ruthenium; Thermodynamics; Water
PubMed: 29884880
DOI: 10.1038/s41467-018-04670-2 -
Journal of the American Chemical Society Sep 2022We report a new general method for trapping short-lived radicals, based on a homolytic substitution reaction S2'. This departure from conventional radical trapping by...
We report a new general method for trapping short-lived radicals, based on a homolytic substitution reaction S2'. This departure from conventional radical trapping by addition or radical-radical cross-coupling results in high sensitivity, detailed structural information, and general applicability of the new approach. The radical traps in this method are terminal alkenes possessing a nitroxide leaving group (, allyl-TEMPO derivatives). The trapping process thus yields stable products which can be stored and subsequently analyzed by mass spectrometry (MS) supported by well-established techniques such as isotope exchange, tandem MS, and high-performance liquid chromatography-MS. The new method was applied to a range of model radical reactions in both liquid and gas phases including a photoredox-catalyzed thiol-ene reaction and alkene ozonolysis. An unprecedented range of radical intermediates was observed in complex reaction mixtures, offering new mechanistic insights. Gas-phase radicals can be detected at concentrations relevant to atmospheric chemistry.
Topics: Alkenes; Chromatography, High Pressure Liquid; Sulfhydryl Compounds; Tandem Mass Spectrometry
PubMed: 36001076
DOI: 10.1021/jacs.2c03618 -
Journal of the American Chemical Society Dec 2021The dehydroacylation of ketones to olefins is realized under mild conditions, which exhibits a unique reaction pathway involving aromatization-driven C-C cleavage to...
The dehydroacylation of ketones to olefins is realized under mild conditions, which exhibits a unique reaction pathway involving aromatization-driven C-C cleavage to remove the acyl moiety, followed by Cu-mediated oxidative elimination to form an alkene between the α and β carbons. The newly adopted '-methylpicolinohydrazonamide (MPHA) reagent is key to enable efficient cleavage of ketone C-C bonds at room temperature. Diverse alkyl- and aryl-substituted olefins, dienes, and special alkenes are generated with broad functional group tolerance. Strategic applications of this method are also demonstrated.
Topics: Acylation; Alkenes; Catalysis; Copper; Hydrazones; Indicators and Reagents; Ketones
PubMed: 34807585
DOI: 10.1021/jacs.1c09587 -
Yakugaku Zasshi : Journal of the... 2019New meta-arylene ethynylene foldamers were developed by employing pyridine and phenol units. These demonstrated interesting properties related to the hydrogen-bonding... (Review)
Review
New meta-arylene ethynylene foldamers were developed by employing pyridine and phenol units. These demonstrated interesting properties related to the hydrogen-bonding behavior of the arylene units. Pyridine-acetylene-phenol foldamers showed improved saccharide recognition abilities compared with pyridine-acetylene foldamers with no phenol units. Solid-liquid extraction could be achieved due to the strong binding. Hydrocarbon stapling by alkene metathesis under templation was attempted, and the helical structure was efficiently stabilized. Phenol-acetylene oligomers spontaneously formed helical structures via intramolecular hydrogen bonding. The helical sense could be biased by adding chiral amines.
Topics: Acetylene; Alkenes; Glucose; Hydrocarbons; Hydrogen Bonding; Macromolecular Substances; Molecular Conformation; Monosaccharides; Organic Chemistry Phenomena; Phenol; Pyridines; Solid Phase Extraction
PubMed: 30930394
DOI: 10.1248/yakushi.18-00179-2 -
Angewandte Chemie (International Ed. in... Oct 2022The incorporation of the gem-difluoromethylene (CF ) group into organic frameworks is highly sought due to the influence of this unit on the physicochemical and...
The incorporation of the gem-difluoromethylene (CF ) group into organic frameworks is highly sought due to the influence of this unit on the physicochemical and pharmacological properties of molecules. Herein we report an operationally simple, mild, and switchable protocol to access various gem-difluoro compounds that employs chlorodifloroacetic anhydride (CDFAA) as a low-cost and versatile fluoroalkylating reagent. Detailed mechanistic studies revealed that electron-transfer photocatalysis triggers mesolytic cleavage of a C-Cl bond generating a gem-difluoroalkyl radical. In the presence of alkene, this radical species acts as a unique intermediate that, under solvent-controlled reaction conditions, delivers a wide range of gem-difluorinated γ-lactams, γ-lactones, and promotes oxy-perfluoroalkylation. These protocols are flow- and batch-scalable, possess excellent chemo- and regioselectivity, and can be used for the late-stage diversification of complex molecules.
Topics: Alkenes; Anhydrides; Lactams; Lactones; Solvents
PubMed: 35997088
DOI: 10.1002/anie.202209143 -
Science (New York, N.Y.) Mar 2021Dearomative cycloaddition reactions represent an ideal means of converting flat arenes into three-dimensional architectures of increasing interest in medicinal...
Dearomative cycloaddition reactions represent an ideal means of converting flat arenes into three-dimensional architectures of increasing interest in medicinal chemistry. Quinolines, isoquinolines, and quinazolines, despite containing latent diene and alkene subunits, are scarcely applied in cycloaddition reactions because of the inherent low reactivity of aromatic systems and selectivity challenges. Here, we disclose an energy transfer-mediated, highly regio- and diastereoselective intermolecular [4 + 2] dearomative cycloaddition reaction of these bicyclic azaarenes with a plethora of electronically diverse alkenes. This approach bypasses the general reactivity and selectivity issues, thereby providing various bridged polycycles that previously have been inaccessible or required elaborate synthetic efforts. Computational studies with density functional theory elucidate the mechanism and origins of the observed regio- and diastereoselectivities.
Topics: Alkenes; Catalysis; Cycloaddition Reaction; Energy Transfer; Hydrocarbons, Aromatic; Molecular Structure; Quinolines; Stereoisomerism
PubMed: 33766881
DOI: 10.1126/science.abg0720 -
Angewandte Chemie (International Ed. in... Jun 2022Palladium(II)-catalyzed C(alkenyl)-H alkenylation enabled by a transient directing group (TDG) strategy is described. The dual catalytic process takes advantage of...
Palladium(II)-catalyzed C(alkenyl)-H alkenylation enabled by a transient directing group (TDG) strategy is described. The dual catalytic process takes advantage of reversible condensation between an alkenyl aldehyde substrate and an amino acid TDG to facilitate coordination of the metal catalyst and subsequent C(alkenyl)-H activation by a tailored carboxylate base. The resulting palladacycle then engages an acceptor alkene, furnishing a 1,3-diene with high regio- and E/Z-selectivity. The reaction enables the synthesis of enantioenriched atropoisomeric 2-aryl-substituted 1,3-dienes, which have seldom been examined in previous literature. Catalytically relevant alkenyl palladacycles were synthesized and characterized by X-ray crystallography, and the energy profiles of the C(alkenyl)-H activation step and the stereoinduction model were elucidated by density functional theory (DFT) calculations.
Topics: Alkenes; Catalysis; Palladium
PubMed: 35467792
DOI: 10.1002/anie.202203624 -
Applied and Environmental Microbiology Sep 2011Bacterial degradation pathways of fuel oxygenates such as methyl tert-butyl and tert-amyl methyl ether (MTBE and TAME, respectively) have already been studied in some...
Bacterial degradation pathways of fuel oxygenates such as methyl tert-butyl and tert-amyl methyl ether (MTBE and TAME, respectively) have already been studied in some detail. However, many of the involved enzymes are still unknown, and possible side reactions have not yet been considered. In Aquincola tertiaricarbonis L108, Methylibium petroleiphilum PM1, and Methylibium sp. strain R8, we have now detected volatile hydrocarbons as by-products of the degradation of the tert-alkyl ether metabolites tert-butyl and tert-amyl alcohol (TBA and TAA, respectively). The alkene isobutene was formed only during TBA catabolism, while the beta and gamma isomers of isoamylene were produced only during TAA conversion. Both tert-alkyl alcohol degradation and alkene production were strictly oxygen dependent. However, the relative contribution of the dehydration reaction to total alcohol conversion increased with decreasing oxygen concentrations. In resting-cell experiments where the headspace oxygen content was adjusted to less than 2%, more than 50% of the TAA was converted to isoamylene. Isobutene formation from TBA was about 20-fold lower, reaching up to 4% alcohol turnover at low oxygen concentrations. It is likely that the putative tert-alkyl alcohol monooxygenase MdpJ, belonging to the Rieske nonheme mononuclear iron enzymes and found in all three strains tested, or an associated enzymatic step catalyzed the unusual elimination reaction. This was also supported by the detection of mdpJK genes in MTBE-degrading and isobutene-emitting enrichment cultures obtained from two treatment ponds operating at Leuna, Germany. The possible use of alkene formation as an easy-to-measure indicator of aerobic fuel oxygenate biodegradation in contaminated aquifers is discussed.
Topics: Alcohols; Alkenes; Betaproteobacteria; DNA, Bacterial; Ethers; Mixed Function Oxygenases; Molecular Sequence Data; Oxygen; Sequence Analysis, DNA
PubMed: 21742915
DOI: 10.1128/AEM.00093-11