Metal-free synthesis of 3,3-disubstituted oxindoles via 1,2-alkylarylation of activated alkenes with alcohols

Metal-free synthesis of 3,3-disubstituted oxindoles utilizing N-arylacrylamides and simple alcohols is developed. It provides an efficient method for preparing a series of hydroxyl-containing oxindole derivatives. This reaction is proposed to proceed through oxidative radical cyclization mechanism. The remarkable features of the reaction are metal-free condition and excellent functional group tolerance.     

Iodo-carbocyclization of electron-deficient alkenes: synthesis of oxindoles and spirooxindoles

Cyclisative carbo-iodination of N-alkyl-N-arylacrylamide derivatives (3) in the presence of PhI(OAc)(2)/I(2) afforded functionalized 3-(iodomethyl)-3-substituted-indolin-2-ones (4) in good to excellent yields. With a suitably functionalized linear amide, spirooxindole 8 was prepared in a one-pot fashion via a sequence of iodo-arylation followed by an in situ base-promoted intramolecular S(N)2 reaction.     

Palladium-catalyzed oxidative arylalkylation of activated alkenes: dual C-H bond cleavage of an arene and acetonitrile

Not one but two: The title reaction proceeds through the dual C-H bond cleavage of both aniline and acetonitrile. The reaction affords a variety of cyano-bearing indolinones in excellent yield. Mechanistic studies demonstrate that this reaction involves a fast arylation of the olefin and a rate-determining C-H activation of the acetonitrile.     

Mechanism of cis-dihydroxylation and epoxidation of alkenes by highly H(2)O(2) efficient dinuclear manganese catalysts

In the presence of carboxylic acids the complex [Mn(IV)2(micro-O)3(tmtacn)2]2+ (1, where tmtacn = N,N',N'-trimethyl-1,4,7-triazacyclononane) is shown to be highly efficient in catalyzing the oxidation of alkenes to the corresponding cis-diol and epoxide with H2O2 as terminal oxidant. The selectivity of the catalytic system with respect to (w.r.t.) either cis-dihydroxylation or epoxidation of alkenes is shown to be dependent on the carboxylic acid employed. High turnover numbers (t.o.n. > 2000) can be achieved especially w.r.t. cis-dihydroxylation for which the use of 2,6-dichlorobenzoic acid allows for the highest t.o.n. reported thus far for cis-dihydroxylation of alkenes catalyzed by a first-row transition metal and high efficiency w.r.t. the terminal oxidant (H2O2). The high activity and selectivity is due to the in situ formation of bis(micro-carboxylato)-bridged dinuclear manganese(III) complexes. Tuning of the activity of the catalyst by variation in the carboxylate ligands is dependent on both the electron-withdrawing nature of the ligand and on steric effects. By contrast, the cis-diol/epoxide selectivity is dominated by steric factors. The role of solvent, catalyst oxidation state, H2O, and carboxylic acid concentration and the nature of the carboxylic acid employed on both the activity and the selectivity of the catalysis are explored together with speciation analysis and isotope labeling studies. The results confirm that the complexes of the type [Mn2(micro-O)(micro-R-CO2)2(tmtacn)2]2+, which show remarkable redox and solvent-dependent coordination chemistry, are the resting state of the catalytic system and that they retain a dinuclear structure throughout the catalytic cycle. The mechanistic understanding obtained from these studies holds considerable implications for both homogeneous manganese oxidation catalysis and in understanding related biological systems such as dinuclear catalase and arginase enzymes.     

A new and facile synthesis of 3(2H)-furanones via carboxylation- decarboxylation sequence

One-pot synthesis of 3(2H)-furanones from α-ethynyl tertiary alcohols and acyl halides has been achieved in the presence of a palladium complex under CO₂ pressure.     

Pd-catalyzed one-pot coupling of allylamines, activated alkenes, and unsaturated halides (or triflate): an atom efficient synthesis of highly functionalized pyrrolidines

A Pd-catalyzed three-component assembling of highly functionalized 4-benzyl-(and allyl-)pyrrolidines was achieved based on a combination of allyl amines, gem-diactivated alkenes, and unsaturated halides (or triflate).     

Highly efficient asymmetric synthesis of fluvirucinine A1 via Zr-catalyzed asymmetric carboalumination of alkenes (ZACA)-lipase-catalyzed acetylation tandem process

ZACA-lipase-catalyzed acetylation tandem process has been shown to proceed satisfactorily with either TBS-protected 4-penten-1-ol or 3-buten-1-ol to provide the corresponding enantiomerically pure (R)-2-ethyl-1-alkanols. Either (R)-5 or (R)-6 was converted to 3 in seven steps. The other fragment 4 was synthesized in nine steps from (-)-(S)-citronellol. Conversion of 3 and 4 into 99% pure fluvirucinine A1 was achieved in four steps via amidation-ring closing metathesis, the overall yield in the longest linear sequence being 34% (13 steps).     

Organocatalyzed route to enantioenriched pipecolic esters: decarboxylation of an aminomalonate hemiester

Enantioenriched pipecolic esters were prepared in good yields in the decarboxylation, at room temperature, of N-protected piperidinohemimalonates catalyzed by cinchona alkaloids. Enantiomeric excesses as high as 72% were obtained when using 9-epi-cinchonine and the N-benzoyl substituted piperidinohemimalonate. A detailed study of the different reaction parameters revealed that the selectivity of this noncovalent organocatalyzed reaction is strongly dependent on the solvent, toluene or carbon tetrachloride being the best ones. The whole process based on the malonic acid synthesis was successfully tested on a 10 mmolar scale and established a practical alternative to the asymmetric protonation of lithium enolates.     

An efficient synthesis of 2-alkylpyridines using an alkylation/double decarboxylation strategy

We have discovered a novel route for synthesising 2-alkylpyridines by exploiting the decarboxylation of pyridyl malonate esters. Herein we report the synthesis of a number of examples and describe how the reaction was discovered.     

Highly efficient synthesis of terminal alkenes from ketones

[reaction: see text] The rhodium(I)-catalyzed methylenation of ketones using trimethylsilyldiazomethane proceeds to give the corresponding alkenes in good yields (60-97%). The use of an excess of 2-propanol and 1,4-dioxane as a solvent were instrumental to obtain the desired alkenes in high yields. Superior results were achieved with the rhodium(I)-catalyzed methylenation in comparison with the standard Wittig reaction.     

The reactions of O(3P) with terminal alkenes: the H2CO channel via 3,2 H-atom shift

The step-scan time-resolved FTIR emission spectroscopy is used to characterize systematically the H(2)CO channel for the reactions of O((3)P) with various alkenes. IR emission bands due to the products of CO, CO(2), and H(2)CO have been observed in the spectra. H(2)CO is identified to be the primary reaction product whereas CO and CO(2) are secondary reaction products of O((3)P) with alkenes. A general trend is observed in which the fraction yield of the H(2)CO product increases substantially as the reactant alkene varies from C(2)H(4), C(3)H(6), 1-C(4)H(8), iso-C(4)H(8), to 1-C(5)H(10). The formation mechanism of the H(2)CO is therefore elucidated to arise from a 3,2 H-atom shift followed by breaking of the C(1)-C(2) bond in the initially formed energized diradical RCH(2)CHCH(2)O*. The 3,2 H-atom shift may become the dominant process with the more rapid delocalization of the energy when the hydrocarbon chain of the alkene molecule is lengthened.     

Three-component synthesis of new unsymmetrical oxindoles via Friedel-Crafts type reaction

The synthesis of 2-(3-(4-(dimethylamino)phenyl)-2-oxoindolin-3-yl)-1H-indene-1,3(2H)-diones as new unsymmetrical oxindoles via a Friedel-Crafts type three-component reaction of 1,3-indandion, N,N-dimethylaniline and isatins in ethanol in the presence of LiClO₄ is reported.     

PhI(OTf)2 Does Not Exist (Yet)**

PhI(OTf)₂ has been used for the past 30 years as a strong I(III) oxidant for organic and inorganic transformations. It has been reported to be generated in situ from the reactions of either PhI(OAc)₂ or PhI=O with two equivalents of trimethylsilyl trifluoromethanesulfonate (TMS-OTf). In this report it is shown that neither of these reactions generate a solution with spectroscopic data consistent with PhI(OTf)₂, with supporting theoretical calculations, and thus this compound should not be invoked as the species acting as the oxidant for transformations that have been associated with its use.     

One-step synthesis of epoxy(perfluoroalkyl)alkenes

Epoxy(perfluoroalkyl)alkenes were synthesized in one step by reaction of perfluoroalkyl iodides with 2-(allyloxymethyl)oxirane and 2-(oct-7-en-1-yl)oxirane in the presence of sodium dithionite and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) under mild conditions.     

Allylic oxidation: easy synthesis of alkenones from activated alkenes with TEMPO

Activated alkenes and dienes are converted into the corresponding alkenone in excellent yields (>90%). In aqueous acetonitrile, the transformations are catalyzed by 2,2,6,6-tetramethyl-1-oxopiperidinium (TEMPO⁺) in the presence of water and 2,6-lutidine. TEMPO⁺ cations were regenerated electrochemically from the radical parent (TEMPO) at a vitreous carbon anode.     

MnSb2O6-chitosan nanocomposite: An efficient catalyst for the synthesis of coumarins via Pechmann reaction

In this work, MnSb₂O₆-chitosan nanocomposites were synthesized and have been employed in Pechmann condensation for the synthesis of coumarin derivatives. MnSb₂O₆-chitosan nanocomposites were characterized by Fourier transform infrared (FTIR), X-ray powder diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDX) techniques. The particles of MnSb₂O₆-chitosan have uniform spheres with sizes that are less than 100 nm. Simplicity, easy work-up, and short reaction times are advantages of this reaction. Also, we evaluated the antibacterial activity for some of the products, and the result showed significant pharmaceutical activities as antibacterial reagents against Staphylococcus aureus and Escherichia coli.     

Mild and efficient synthesis of (Z)-alpha-chloroalkylidene-beta-lactones via the PdCl2-catalyzed cyclocarbonylation of 2-alkynols

[reaction: see text] A mild and efficient methodology involving PdCl(2)-catalyzed cyclocarbonylation of 2-alkynols with CuCl(2) for the synthesis of (Z)-alpha-chloroalkylidene-beta-lactones was developed. Using the readily available optically active propargylic alcohols allows convenient synthesis of the corresponding (Z)-alpha-chloroalkylidene-beta-lactones with high ee values. cis-Chloropalladation was observed as the major pathway, which is unique as compared to the reported data.     

Mild and efficient functionalization of hydrogen-terminated Si(111) via sonochemical activated hydrosilylation

Efficient chemical functionalization of hydrogen-terminated Si(111) with simple and bifunctional 1-alkenes was achieved via novel sonochemical activated hydrosilylation, utilizing just a simple ultrasonic bath. It is an extremely mild method that allows the specific attachment of unprotected bifunctional alkenes such as undecenol, undecylenic acid, and even a heat/UV-sensitive alkene, bearing an activated leaving group (N-succinimidyl undecylenate), without suffering any degradation.