RESUMEN
A series of chiral ligands were synthesized using chloramphenicol base as starting materials. These ligands were applied to the asymmetric catalytic reactions of terminal alkynes with aldehydes to obtain a propargyl alcohol product in high yield (80-94%) with excellent enantioselectivities (82-96%).
RESUMEN
Reported herein is a reactivity of propargyl alcohols as "Three-Carbon Synthons" in a Rh(III)-catalyzed C-H functionalization of acetanilides, leading to the synthesis of core structures of isocryptolepine, γ-carbolines, dihydrochromeno[2,3-b]indoles, and diindolylmethanes (DIM) derivatives. The transformation involves a rhodium(III)-catalyzed C-H functionalization and heteroannulation to yield indoles followed by a cascade cyclization with both external and internal nucleophiles to afford diverse products. The role of the hydroxy group, the key function of the silver additive, the origin of the reverse regioselectivity and the rate-determining step, are rationalized in conformity with the combination of experimental, noncovalent interaction analysis and DFT studies. This protocol is endowed with several salient features, including one-pot multistep cascade approach, exclusive regioselectivity, good functional group tolerance and synthesis of variety of molecular frameworks.
RESUMEN
The C-H functionalization strategy provides access to valuable molecules that previously required convoluted synthetic attempts. Dual C-H unsymmetrical functionalization, with a single bifunctional reagent, is an effective tactic. Propargyl alcohols (PAs), despite containing a reactive C≡C bond, have not been explored as building blocks via oxidative cleavage. Annulations via C-H activation are a versatile and synthetically attractive strategy. We disclose PA as a new bifunctional reagent for unsymmetrical dual C-H functionalization of biphenylamine for regioselectively annulated outcomes. On tuning the conditions, the annulation bifurcated towards an unusual dual oxidative cyclization. This method accommodates a wide range of PAs and showcases late-stage diversification of some natural products.
RESUMEN
Natural lipases typically recognize enantiomers of alcohols based on the size differences of substituents near the carbinol moiety and selectively react with the R enantiomers of secondary alcohols. Therefore, lipase-catalyzed dynamic kinetic resolution (DKR) of racemic secondary alcohols produces only R enantiomers. We report herein a method for obtaining S enantiomers by DKR of secondary 3-(trialkylsilyl)propargyl alcohols by using a well-known R-selective Pseudomonas fluorescens lipase in combination with a racemization catalyst VMPS4, in which the silyl group reverses the size relationship of substituents near the carbinol moiety. We have already reported R-selective DKR of the corresponding propargyl alcohols without substituents on the ethynyl terminal carbon, and the presence of an easily removable silyl group has enabled us to produce both enantiomers of propargyl alcohols in high chemical yields and with high enantiomeric excess. In addition, immobilization of the lipase on Celite was found to be important for achieving a high efficiency of the DKR.
Asunto(s)
Tierra de Diatomeas , Metanol , Estereoisomerismo , Alcoholes , Lipasa/metabolismo , Cinética , Catálisis , CarbonoRESUMEN
Gold-catalyzed transformations of 1,3-diarylpropargyl alcohols and various aryl nucleophiles were studied. Selective tunable synthetic methods were developed for 1,1,3-triarylallenes, diaryl-indenes and tetraaryl-allyl target products by C3 nucleophilic substitution and subsequent intra- or intermolecular hydroarylation, respectively. The reactions were scoped with regards to gold(I)/(III) catalysts, solvent, temperature, and electronic and steric effects of both the diarylpropargyl alcohol and the aryl nucleophiles. High yields of triaryl-allenes and diaryl-indenes by gold(III) catalysis were observed. Depending on the choice of aryl nucleophile and control of reaction temperature, different product ratios have been obtained. Alternatively, tetraaryl-allyl target products were formed by a sequential one-pot tandem process from appropriate propargyl substrates and two different aryl nucleophiles. Corresponding halo-arylation products (I and Br; up to 95 % 2-halo-diaryl-indenes) were obtained in a one-pot manner in the presence of the respective N-halosuccinimides (NIS, NBS).
Asunto(s)
Oro , Indenos , Alcoholes/química , Catálisis , Oro/química , EstereoisomerismoRESUMEN
Here we report the synthesis of interesting 3-alkyl-4-hydroxy-1-aryl-4-(propa-1,2-dienyl)1H-pyrazol-5(4H)-ones and 9-alkyl-7-aryl-1-oxa-7,8-diazaspiro[4.4]nona-3,8-dien-6-ones, starting from 1,2-diaza-1,3-dienes (DDs) and propargyl alcohol. The reaction proceeds through a sequence Michael-type nucleophilic attack/cyclization/[2,3]-Wittig rearrangement. In the same way, the reaction between the aforementioned DDs and allyl alcohol furnished 4-allyl-4-hydroxy-3-alkyl-1-aryl-1H-pyrazol-5(4H)-ones. A DFT study was also carried out, in order to have decisive clarifications about the mechanism.
RESUMEN
In this work, we treated chitin with 2-(azidomethyl)oxirane and successfully involved the resultant azido chitin derivatives in the ultrasound-assisted Cu(I)-catalyzed azido-alkyne click (CuAAC) reaction with propargylic ester of N,N,N-trimethyl glycine. Thus, we obtained novel water-soluble triazole chitin derivatives. The triazole chitin derivatives and their nanoparticles are characterized by a high in vitro antibacterial activity, which is the same or even higher than that of commercial antibiotics ampicillin and gentamicin. The obtained derivatives are non-toxic. Moreover, the obtained water-soluble polymers are highly efficient green catalysts for the aldol reaction in green solvent water. The catalysts can be easily extracted from the reaction mixture by its precipitation with green solvent ethanol followed by centrifugation and they can be reused at least 10 times.
Asunto(s)
Antibacterianos/química , Quitosano/síntesis química , Quitosano/farmacología , Óxido de Etileno/química , Nanopartículas/química , Triazoles/química , Aldehídos/química , Ampicilina/química , Exoesqueleto , Animales , Antiinfecciosos , Catálisis , Química Clic , Ésteres , Gentamicinas/química , Tecnología Química Verde , Iones , Espectroscopía de Resonancia Magnética , Solubilidad , Solventes , ViscosidadRESUMEN
One palladium-catalyzed sequential coupling reactions were successfully used as a new protocol for the synthesis of unsymmetrical 2,3-diethynyl quinoxalines and 4-ethynyl-substituted pyrrolo[1,2-a]quinoxalines. The one-pot two coupling reactions of 2,3-dichloroquinoxaline, with two different terminal alkynes, under controlled conditions produced selectively unsymmetrical 2,3-diethynyl quinoxalines with high yields. When one of the two terminal alkynes was 3-propyne-1-ol, in the presence of secondary amines, cyclization occurred and 4-ethynyl-substituted pyrrolo[1,2-a]quinoxalines were successfully formed. All synthesized compounds were tested against the two bacterial strains including Micrococcus luteus and Pseudomonas aeruginosa.
Asunto(s)
Antibacterianos , Pirroles , Quinoxalinas , Antibacterianos/síntesis química , Antibacterianos/química , Antibacterianos/farmacología , Catálisis , Micrococcus luteus/efectos de los fármacos , Micrococcus luteus/crecimiento & desarrollo , Paladio/química , Pseudomonas aeruginosa/efectos de los fármacos , Pseudomonas aeruginosa/crecimiento & desarrollo , Pirroles/síntesis química , Pirroles/química , Pirroles/farmacología , Quinoxalinas/síntesis química , Quinoxalinas/química , Quinoxalinas/farmacologíaRESUMEN
The powerful nature of the secondary ion mass spectrometry (SIMS) technique was explored in order to analyse very thin surface layers that were self-assembled on steel material from acidic solution. These surface layers are adsorbed corrosion inhibitors. The SIMS technique proved useful to characterise the molecular structure and homogeneity of thin surface layers in the nanometre range of specific analytes on the metallic substrate. Using SIMS, the thermal stability of these layers was further investigated and the desorption energy at a certain temperature was determined, where special attention was devoted to the method's static limit. In order to compare, and for certain cases emphasise, the benefits gained by using SIMS in such surface analysis compared with the X-ray photoelectron spectroscopy (XPS) method, the same samples were also analysed by means of the latter. XPS is usually considered to be the most powerful analytical tool in surface analysis studies, but, as shown herein, it has certain limitations compared to SIMS. Finally, the surface topography was investigated by employing atomic force microscopy (AFM) in order to carry out a comprehensive surface analysis. Graphical Abstract á .
RESUMEN
The reactions of several 2-chloroquinoline-3-carboxylate esters with propargyl alcohol and a secondary amine in the presence of palladium catalyst leads to the formation of new alkyl 1-amino substituted pyrrolo[1,2-a]quinoline-4-carboxylate derivatives. This one-pot process, carried out in the absence of any copper salt, provides an efficient method for the synthesis of functionalized pyrrolo[1,2-a]quinolines in good-to-high yields.
Asunto(s)
Ácidos Carboxílicos/química , Quinolinas/química , Quinolinas/síntesis química , Alquinos/química , Catálisis , Técnicas de Química Sintética , ÉsteresRESUMEN
The reaction of propargyl alcohol with hydroxyl radical has been studied extensively at CCSD(T)/aug-cc-pVTZ//MP2/cc-pVTZ level. This is the first time to gain a conclusive insight into the reaction mechanism and kinetics for this important reaction in detail. Two reaction mechanisms were revealed, namely addition/elimination and hydrogen abstraction mechanism. The reaction mechanism confirms that OH addition to C≡C triple bond forms the chemically activated adducts, IM1 (·CHCOHCH2OH) and IM2 (CHOH·CCH2OH), and the hydrogen abstraction pathways (-CH2OH bonded to the carbon atom and alcohol hydrogen) may occur via low barriers. Harmonic model of Rice-Ramsperger-Kassel-Marcus theory and variational transition state theory are used to calculate the overall and individual rate constants over a wide range of temperatures and pressures. The calculated rate constants are in good agreement with the experimental data. At atmospheric pressure with Ar as bath gas, IM1 (·CHCOHCH2OH) and IM2 (CHOH·CCH2OH) formed by collisional stabilization are dominant in the low temperature range. The production of CHCCHOH + H2O via hydrogen abstraction becomes dominate at higher temperature. The fraction of IM3 (CH2COHCH2·O) is very significant over the moderate temperature range.
Asunto(s)
Alquinos/química , Gases/química , Radical Hidroxilo/química , Modelos Químicos , Propanoles/químicaRESUMEN
Propargyl alcohol (PA) is a high production volume chemical used in synthesis of many industrial chemicals and agricultural products. Despite the potential for prolonged or accidental exposure to PA in industrial settings, the toxicity potential of PA was not well characterized. To address the knowledge gaps relevant to the toxicity profile of PA, the National Toxicology Program (NTP) conducted 2-week, 14-week and 2-year studies in male and female F344/N rats and B6C3F1/N mice. For the 2-week inhalation study, the rats and mice were exposed to 0, 31.3, 62.5, 125, 250 or 500ppm. Significant mortality was observed in both rats and mice exposed to ≥125ppm of PA. The major target organ of toxicity in both mice and rats was the liver with exposure-related histopathological changes (250 and 500ppm). Based on the decreased survival in the 2-week study, the rats and mice were exposed to 0, 4, 8, 16, 32 or 64ppm of PA in the 14-week study. No treatment-related mortality was observed. Mean body weights of male (≥8ppm) and female mice (32 and 64ppm) were significantly decreased (7-16%). Histopathological changes were noted in the nasal cavity, and included suppurative inflammation, squamous metaplasia, hyaline droplet accumulation, olfactory epithelium atrophy, and necrosis. In the 2-year inhalation studies, the rats were exposed to 0, 16, 32 and 64ppm of PA and the mice were exposed to 0, 8, 16 and 32ppm of PA. Survival of male rats was significantly reduced (32 and 64ppm). Mean body weights of 64ppm male rats were significantly decreased relative to the controls. Both mice and rats showed a spectrum of non-neoplastic changes in the nose. Increased neoplastic incidences of nasal respiratory/transitional epithelial adenoma were observed in both rats and mice. The incidence of mononuclear cell leukemia was significantly increased in male rats and was considered to be treatment-related. In conclusion, the key findings from this study indicated that the nose was the primary target organ of toxicity for PA. Long term inhalation exposure to PA led to nonneoplastic changes in the nose, and increased incidences of respiratory/transitional epithelial adenomas in both mice and rats. Increased incidences of harderian gland adenoma may also have been related to exposure to PA in male mice.