RESUMO
The silver hexafluoroantimonate/ N-bromosuccinimide (NBS)-catalyzed synthesis of α-alkylated aryl ketones with a tertiary carbon center from internal alkynes and benzyl alcohols is reported. This reaction proceeds via the etherification of benzyl alcohols with an in situ generated benzyl bromide, formed by the reaction of benzyl alcohol with a catalytic amount of NBS and AgSbF6. Ag-catalyzed C-O cleavage of the ether leads to a tolyl radical, which undergoes addition to the alkyne, ultimately leading to the α-alkylated aryl ketone products.
RESUMO
Without the requirement for base or other additives, Co2Rh2/C can selectively catalyze both mono- and bis-N-alkylation through the coupling of simple alcohols with amines, yielding a range of secondary and tertiary amines in good to excellent isolated yields. The reaction can be applied to benzyl alcohol with optically active 1-phenylethan-1-amines, and secondary amines were isolated in quantitative yields with an excellent enantiomeric excess (ee > 94%). Selectivity is achieved by varying the reaction temperature and amount of catalyst used. This catalytic system has several advantages including eco-friendliness and a simple workup procedure. The catalyst can be successfully recovered and reused ten times without any significant loss of activity.
RESUMO
The [Rh(COD)Cl]2/xantphos/Cs2CO3 system efficiently catalyzes the reductive N-alkylation of aryl nitro compounds with alcohols by a borrowing-hydrogen strategy to afford the corresponding imine products in good to excellent yields. In the absence of xantphos, the [Rh(COD)Cl]2/Cs2CO3 catalytic system behaves as an effective catalyst for the dehydrogenative coupling of alcohols to esters, with nitrobenzene as a hydrogen acceptor. The reactivity of the rhodium catalytic system can be easily manipulated to selectively afford the imine or ester.
RESUMO
A cobalt-rhodium heterobimetallic nanoparticle (Co2Rh2/C)-catalyzed tandem reductive amination of aldehydes with nitroaromatics to sec-amines has been developed. The tandem reaction proceeds without any additives under mild conditions (1 atm H2 and 25 °C). This procedure can be scaled up to the gram scale, and the catalyst can be reused more than six times without loss of activity.
RESUMO
Poly(3,4-dimethyl-5-vinylthiazolium) iodide was used as a polymer precatalyst in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and phenazine for the oxidative esterification of aldehydes with alcohols. Selective functionalization of OH groups was achieved in the presence of NH2 groups. The poly(thiazolium) iodide/DBU/phenazine system exhibited excellent catalytic activity and could be reused five times without loss of activity.
RESUMO
An unprecedented oxidative dimerization by palladium catalysis has been developed using PhI(OPiv)2 as a by-standing oxidant. This provides a facile method for the synthesis of quaternary 2,3'-bibenzofuran-2'(3')-ones from readily accessible substrates. A plausible mechanism involving a Pd(II)-Pd(IV) catalytic cycle is proposed; a trace amount of water is required for subsequent oxidation.
RESUMO
A highly regioselective rhodium-catalyzed intermolecular carbonylative [2 + 2 + 1] cycloaddition of alkynes using alcohol as a CO surrogate to access 4-methylene-2-cyclopenten-1-ones has been developed. In this transformation, the alcohol performs multiple roles, including generating the Rh-H intermediate, functioning as the CO source, and assisting in the isomerization of the alkyne. Alkynes can act as both the olefin and the alkyne partner in the cyclopentenone core.
RESUMO
A cobalt-rhodium heterobimetallic nanoparticle-catalyzed reductive cyclization of 2-(2-nitroaryl)acetonitriles to indoles has been achieved. The tandem reaction proceeds without any additives under the mild conditions (1 atm H2 and 25 °C). This procedure could be scaled up to the gram scale. The catalytic system is significantly stable under these reaction conditions and could be reused more than ten times without loss of catalytic activity.
RESUMO
A protocol involving facile sequential C(sp(3))-H and C(sp(2))-H activation reactions of 3-alkylbenzofurans catalyzed by Pd(OAc)2 in the presence of pivalic acid, silver salt, and tricyclohexylphosphine 'on water' was developed. Aryl iodides were used as substrates in a tandem bisarylation reaction to generate 3-arylalkyl-2-arylbenzofurans in moderate to high yields at room temperature. The reaction revealed in this study is a rare example of consecutive C(sp(3))-H and C(sp(2))-H bond activation under mild reaction conditions.
Assuntos
Benzofuranos/química , Paládio/química , Água/química , Catálise , TemperaturaRESUMO
The Pd-catalyzed bisarylation of pyrroles with aryl iodides on water is described. The reaction proceeds under mild reaction conditions, i.e., relatively low temperature (40 °C) and phosphine-free.
RESUMO
A novel Rh-catalyzed carbonylative [3 + 2 + 1] cycloaddition of alkyne-tethered alkylidenecyclopropanes for the facile synthesis of bicyclic phenols in high yields has been developed. The reaction tolerated carbon and heteroatoms in the tether.
RESUMO
A method for the synthesis of bicyclo[4.1.0]heptenes from 1,6-enynes through Pd-catalyzed cycloisomerization has been developed. N- and O-tethered 1,6-enynes were successfully transformed to their corresponding 3-aza- and 3-oxabicyclo[4.1.0]heptenes in reasonable-to-high yields using the catalysts [PdCl2(CH3CN)2]/P(OPh)3 or [Pd(maleimidate)2(PPh3)2] in toluene. The computational calculations using density functional theory indicate that [PdCl2{P(OPh)3}] in the oxidation state Pd(II) acts as the active catalyst species for the formation of 3-azabicyclo[4.1.0]heptenes through 6-endo-dig cyclization.
RESUMO
A cross-coupling reaction between alkyl bromides and chlorides and various Grignard reagents was carried out in the presence of commercially available copper or copper oxide nanoparticles as a catalyst and an alkyne additive. The catalytic system shows high activity, a broad scope, and good functional group tolerance.
RESUMO
Four ruthenium(II) complexes, BPT, BPN, BPPT, and BPPN, have been prepared and characterized by (1)H NMR, (13)C NMR, high resolution mass spectrometry (HRMS), elemental analysis, and X-ray crystallography. All the complexes incorporate a pyridyl unit on the terpyridine-type or N-heterocyclic carbene (NHC) ligand and the pyridyl unit can be protonated upon addition of 1.0 M HCl in diethyl ether. The proton-dependent absorption and luminescence spectrum were measured in CH(3)CN. In the case of BPT, the λ(max)(abs) was moved by 10 nm from 490 nm to 500 nm after the addition of 12 equiv. of HCl and the intensity of the emission spectrum increased. In contrast, in the case of BPN, the λ(max)(abs) was red-shifted by 43 nm from 424 nm to 467 nm and the emission was dramatically quenched upon the addition of the equiv. of HCl. However, there were no noticeable changes in the λ(max)(abs) values of BPPT and BPPN even after the addition of the HCl to a solution of those complexes. Moreover, BPN has a selective sensing property for a proton among many cations.
RESUMO
Bioassay-guided fractionation of an 80% MeOH extract of Juglan sinensis leaves and twigs has resulted in the isolation of three new triterpenes (1-3) and two new sesquiterpenes (4-5) along with two known sesquiterpenes (6-7). The new compounds were determined to be 3ß, 11α, 19α, 24, 30-pentahydroxy-20ß, 28-epoxy-28ß-methoxy-ursane (1), 1α, 3ß-dihydroxy-olean-18-ene (2), 2α, 3α, 23-trihydroxy-urs-12-en-28-oic acid 28-O-ß-d-glucopyranoside (3), (4S, 5S, 7R, 8R, 14R)-8, 11-dihydroxy-2, 4-cyclo-eudesmane (4), 15-hydroxy-α-eudesmol-11-O-ß-d-glucopyranoside (5), by spectroscopic analysis. The cytotoxicity of compounds (1-7) against four cancer cell lines such as B16F10, Hep-2, MCF-7 and U87-MG was evaluated. Compounds 1, 2, 6 and 7 showed potent cytotoxicity against all of four cancer cell lines, respectively.
Assuntos
Antineoplásicos Fitogênicos/química , Antineoplásicos Fitogênicos/farmacologia , Juglans/química , Sesquiterpenos/química , Sesquiterpenos/farmacologia , Triterpenos/química , Triterpenos/farmacologia , Antineoplásicos Fitogênicos/isolamento & purificação , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Humanos , Neoplasias/tratamento farmacológico , Folhas de Planta/química , Sesquiterpenos/isolamento & purificação , Triterpenos/isolamento & purificaçãoRESUMO
Trifluorovinyl groups are introduced onto the cyclopentadienyl ligands of ferrocene at the 1-, 1,1'-, and 1,2-positions by Negishi-type and Stille-type coupling reactions of trifluorovinylzinc chloride and tri-n-butyltrifluorovinyl stannane with several iodoferrocenes. Modification of the trifluorovinyl group by nucleophilic substitution and [2+2] cycloaddition make them versatile building blocks for synthetic transformations. 1,1'-Bis(trifluorovinyl) ferrocene reacts upon contact with silica or oxidizing agents and in the presence of a suitable nucleophile through a redox autocatalytic mechanism to afford ferrocenophanes with fluorinated handles. C(F)(H) and C(F)(OMe) moieties in α-positions allowed further modifications to be performed by nucleophilic substitution of the fluorine atoms. A series of ferrocenes with fluorinated side chains and ferrocenophanes with fluorinated handles were isolated and characterized. Several molecular structures were determined by single-crystal X-ray diffraction. The influence of the fluorine substituents on the redox properties of the iron center were studied by cyclic voltammetry.
RESUMO
Contrary to the stereotype, Jacobsen's catalyst, chiral (salcy)Co(III)OAc adopts an unusual binding mode. The tetradentate {ONNO} ligand does not form a square plane but wraps cobalt in a cis-ß fashion while acetate is chelating.
RESUMO
A single crystal structure of an aluminium-fluoride complex of a model compound (NODA-benzyl) was studied to understand the co-ordination chemistry. Series of ligands with an extra carboxylic acid linker for biomolecule conjugation were studied for improved (18)F-labeling applications.