PubMed Journal Database | The Journal of organic chemistry 
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Showing PubMed Articles 1–25 of 2,000+ from The Journal of organic chemistry
The quenching of peroxyl radicals by ortho-(alkyltelluro)phenols occurs by a more complex mechanism than formal H-atom transfer. In an effort to improve on this concept we have prepared (alkyltelluro)resorcinols and bis(alkyltelluro)phenols and evaluated their catalytic chain-breaking and preventive antioxidative properties. The in situ formed trianion produced from 2-bromophenol and three equivalents of tert-butyllithium was allowed to react with dialkyl ditellurides to provide ortho-(alkyltelluro)phenols...
Two Approaches to the Aromatic Core of the Aminonaphthoquinone Antibiotics.
Two complementary approaches are presented for the synthesis of the quinone chromophores of the naphthoquinone ansamycins and related natural products. The first involves the use of an improved protocol for the manganese(III) acetate mediated cyclization of 5-aryl-1,3-dicarbonyl compounds to β-naphthols, leading to the simple, scalable preparation of building blocks suitable for the synthesis of naturally occurring aminonaphthoquinones. The second approach involves the Diels-Alder reaction of a series of n...
A simple, general route to the 1,2-dihydronaphtho[2,1-b]furans and 2,3-dihydrobenzofurans substituted at C-2 by an acyl or aryl group, starting from phenolic Mannich bases and pyridinium ylides, has been developed. The mechanism of the reaction is believed to involve the formation of the o-quinone methide intermediate, Michael-type addition of the ylide to the o-quinone methide, followed by intramolecular nucleophilic substitution.
A Predictably Selective Nitration of Olefin with Fe(NO3)3 and TEMPO.
Iron nitrate with TEMPO has been applied for regio- and stereoselective nitration of a wide variety of aromatic, aliphatic and heteroaromatic olefins. The reaction provided nitroolefins with trans-selectivity. The present protocol can allow olefin nitration as a method for streamlining complex molecule synthesis.
A protocol has been developed for conducting the palladium-catalyzed reductive carbonylation of aryl iodides and bromides using 9-methylfluorene-9-carbonyl chloride (COgen) as a source of externally delivered carbon monoxide in a sealed two-chamber system (COware), and potassium formate as the in situ hydride source. The method is tolerant to a wide number of functional groups positioned on the aromatic ring, and it can be exploited for the isotope labeling of the aldehyde group. Hence, reductive carbonylat...
The mechanism of the chiral VANOL-BOROX Brønsted acid catalyzed aziridination reaction of imines and ethyldiazoacetate has been studied using a combination of experimental kinetic isotope effects and theoretical calculations. A stepwise mechanism where reversible formation of a diazonium ion intermediate precedes rate-limiting ring closure to form the cis-aziridine is implicated. A revised model for the origin of enantio- and diastereoselectivity is proposed based on relative energies of the ring-closing t...
A stereoselective synthesis of bicyclic primary or secondary amines, based on tetralin or chroman structural moieties, is reported. These amines are precursors of important active pharmaceutical ingredients such as rotigotine (Neupro), robalzotan, and ebalzotan. The key step is based on a multienzymatic reduction of an α,β-unsaturated aldehyde or ketone to give the saturated primary or secondary alcohol, in a high yield and with a high ee. The catalytic system consists of the combination of an ene-reducta...
Two efficient highly regioselective routes for the synthesis of unsymmetrically substituted 1-aryl-3,5-bis(het)arylpyrazoles with complementary regioselectivity starting from active methylene ketones have been reported. In the first protocol, the newly synthesized 1,3-bis(het)aryl-monothio-1,3-diketone precursors (prepared by condensation of active methylene ketones with het(aryl) dithioesters in the presence of sodium hydride) were reacted with arylhydrazines in refluxing ethanol under neutral conditions,...
Gold-catalyzed Reactions between Alkenyldiazo Carbonyl Species and Acetals.
In the presence of catalyst IPrAuSbF6 catalyst (IPr = 1,3-bis(diisopropyl phenyl)imidazol-2-ylidene), alkenyldiazo carbonyl species react with organic acetals to give E-configured alkyl 3,5-dimethoxy-5-pent-2-enoates stereoselectively. This reaction sequence comprises an initial Prins-type reaction, followed by gold carbene formation.
Donor-Acceptor Ferrocenyl Substituted Benzothiadiazoles: Synthesis, Structure and Properties.
This article reports the design, and synthesis of D-pi1-A-pi2-D unsymmetrical, and D-pi1-A-pi2-A-pi1-D symmetrical type of ferrocenyl substituted benzothiadiazoles by the Pd-catalyzed Sonogashira, and Stille coupling reactions. The photophysical, and electrochemical behavior of the ferrocenyl substituted benzothiadiazoles show strong donor-acceptor interaction. The increase in the number of acceptor benzothiadiazole unit, results in the lowering of the energy gap, which leads to the bathochromic shift of th...
Nickel-Catalyzed Suzuki-Miyaura Coupling of Heteroaryl Ethers with Arylboronic Acids.
Nickel-catalyzed Suzuki-Miyaura coupling of heteroaryl ethers with arylboronic acids was described. Selective activation of the phenol C-O bonds was readily achieved by conversion of them into the corresponding aryl 2,4-dimethoxy-1,3,5-triazine-6-yl ethers, in which aryl C-O bond could be selectively cleaved with inexpensive, air- and moisture-stable NiCl2(dppf) as a catalyst. Coupling of these readily accessible heteroaryl ethers proved to be tolerant of extensive functional groups including those electron...
Asymmetric Approach to Hyacinthacines B1 and B2.
Naturally occurring hyacinthacines B1 and B2 have been prepared from a common, easily available, advanced intermediate. The approach features several highly stereoselective transformations: inter alia, a dichloroketene-enol ether [2 + 2] cycloaddition, a Bruylants alkylation, and an amino-nitrile alkylation-reduction.
The selective synthesis of tetrahydroquinolines and fluorinated arylamines was performed in superacid HF/SbF5 through a superelectrophilic ammonium-carbenium activation process. This anti-Markovnikov oriented reaction was applied to the straightforward synthesis of highly valued (fluorinated) nitrogen-containing heterocyclic compounds.
5,10,15,20-Tetraaryl-22-hetero-1,5-naphthiporphyrins, which contain a 1,5-naphthylene moiety instead of one pyrrole embedded in the macrocyclic framework of 21-heteroporphyrins, were obtained by the [3 + 1] approach using the 1,5-naphthylene analogue of tripyrrane (1,5-bis(phenyl(2-pyrolyl)methyl)naphthalene) and 2,5-bis(arylhydroxymethyl)heterocyclopenta-diene (heterocyclopentadiene: thiophene, selenophene, tellurophene). The steric constraints, imposed by the substitution mode of 1,5-naphthylene building...
A mild and efficient method for the synthesis of functionalized 1,5-diene-3-ynes from 1,3-diynes under PdII catalysis is described. The process allows quick and atom-economical assembly of various dihalo-, haloacyl- and diacyl-substituted 1,5-diene-3-ynes in high yields. The switch of selectivity in the formation of these dienyne products can be controlled by the choice of catalysis system and reaction conditions.
Oxadiazoline 6 was synthesized to generate endo-tricyclo[3.2.1.02,4]octan-8-ylidene (3) by either photolysis or thermolysis. Diasteromer 6a thermally decomposed twice as fast as 6b. Carbene 3 was trapped stereoselectively by acrylonitrile and diethylamine in high yields. It behaved as a nucleophilic carbene with electron-poor alkenes, like acrylonitrile, but as an electrophile with very electron-rich species, such as diethylamine. When performing the reactions in cyclohexane and cyclohexene, however, isomer...
Treatment of benzaldehyde and an acetoacetate ester with potassium carbonate in an alcohol solvent proceeds via γ-C-alkylation rather than α-C-alkylation resulting in the formation of 6-phenyl-2,4-dioxotetrahydropyran. Based upon results from deuterium exchange experiments, carbon-13 labeling experiments, (1)H NMR monitoring studies, and reactivity studies, our proposed mechanism for this reaction involves deprotonation at the α-carbon, intramolecular proton transfer to form a γ-anion, addition of the r...
The enantiomer of the bicyclic lomaiviticin aglycone A core was prepared via a two-directional, divergent approach featuring (1) a double Ireland Claisen rearrangement to establish key core bonds with correct relative stereochemistry and (2) a double olefin metathesis reaction to deliver both cyclohexene rings of the target.
A practical one-pot and regiospecific three-component process for the synthesis of 2,3-disubstituted indoles from 2-bromoanilides was developed via consecutive palladium-catalyzed Sonogashira coupling, amidopalladation, and reductive elimination.
In marked contrast to the variety of strategies available for oxidation and nucleophilic functionalization of methylene groups adjacent to amines, relatively few approaches for modification of this position with electrophilic reaction partners have been reported. In the course of an investigation of the reactions of photogenerated α-amino radicals with electrophiles, we made the surprising observation that the efficiency of radical photoredox functionalization of N-aryl tetrahydroisoquinolines is dramatica...
A triple cascade was developed using a simple copper catalyst to trans-selectively access bicyclic isoxazolidines in a one-pot synthesis. This strategy features the in situ generation of nitrones and subsequent trapping by [3 + 2] cycloaddition. In this method, copper serves three catalytic functions: as a Lewis acid for the ene reaction, as an organometallic for aerobic oxidation, and as a Lewis acid for an endo-selective [3 + 2] cycloaddition. The successful merging of aerobic oxidation and Lewis acid cat...
Double reduction of cyclic aromatic sulfonamides: synthesis of (+)-mesembrine and (+)-mesembranol.
The synthesis of (+)-mesembrine (1) and (+)-mesembranol (2) has been achieved from the monoterpene (S)-(-)-perillyl alcohol. Key transformations include a diastereo- and regioselective Pd-mediated intramolecular Heck reaction, and a double reduction of the resultant cyclic sulfonamide, to afford the cis-3a-aryloctahydroindole skeleton.
A practical and safe synthesis of 1,2-bis(trimethylsilyl)benzene from 1,2-dichlorobenzene and Me3SiCl was achieved by use of a hybrid metal of Mg and CuCl in the presence of LiCl in 1,3-dimethyl-2-imidazolidinone (DMI). This method does not require a toxic HMPA, provides a high yield of the product under mild conditions, and is also applied to synthesis of substituted 1,2-bis(trimethylsilyl)benzenes and poly(trimethylsilyl)benzenes.
A series of new isophorone derivatives (1-5), incorporating the heterocyclic ring or aza-crown-ether group, with large Stokes shifts (>140 nm), have been synthesized and characterized. 1-4 display aggregation-induced emission behaviors, while dye 5 is highly emissive in solution but quenched in the solid state. It was found that the tuning of emission color of the isophorone-based compounds in the solid state could be conveniently accomplished by changing the terminal substituent group. The photophysical pr...
A manganese dioxide (MnO2)-methanesulfonic acid (CH3SO3H) oxidation system has been developed to efficiently promote direct coupling of benzylic ethers and carbamates with simple ketones via oxidative C-H bond activation. The alkylation proceeds smoothly under air atmosphere to afford the corresponding products in good to excellent yields (53-87%). The employment of the combination of MnO2 and CH3SO3H is attractive on the basis of economical and environmental issues.
