Synergistic effects of the exo- and endocyclic chiral centers of an imidazolidinone-based auxiliary were investigated in the perspective of acetate aldol reactions. The reversal in diastereoselectivity was accomplished by lithium and titanium enolate reactions, which proceed through proposed open and closed transitions states, respectively. The aldol adducts were used in ...

The first synthesis of the natural products credneramide A and B was accomplished by utilizing Alder-ene reactions between a terminal alkene and an internal alkyne to generate the unusual 1,4-diene substructure of these compounds. Moreover, two different short linear sequences toward these targets are evaluated using either a cobalt-catalyzed Alder-ene ...

We report the oxidation of the first line anti-HIV drug efavirenz (EFV), mediated by a bio-inspired nonheme Fe-complex. Depending upon the experimental conditions this system can be tuned either to yield the major EFV metabolite, 8-hydroxy-EFV, in enantiomerically pure form or to mimic cytochrome P450 (CYP) activity, yielding 8-hydroxy-EFV and ...

The true course of the lithium salt-free Wittig reaction has long been a contentious issue in organic chemistry. Herein we report an experimental effect that is common to all of the three major phosphonium ylide classes (non-stabilized, semi-stabilized and stabilized): there is consistently raised selectivity for cis-oxaphosphetane and its derived ...

Oxidation of a doubly cyclometallated platinum(ii) complex results in two isomeric platinum(iv) complexes. Whereas the trans isomer is robust, being manipulable in air at room temperature, the cis isomer decomposes at -20 °C and above. Reductive coupling of an alkyl chloride at the cis isomer gives a new species which ...

A novel route for anti-deactivation of methanol-to-propylene catalyst has been established through supporting nano-gold on ZSM-5, which efficiently reinforces the catalytic stability due to the effect of gold nanoparticles on the stabilization of dehydrogenation intermediates within the coking process.

A highly diastereo- and enantioselective formal [3 + 2] cycloaddition of α,β-unsaturated esters and 3-hydroxyoxindoles catalyzed by a dinuclear zinc-ProPhenol complex is reported. The stereoselective Michael additions of 3-hydroxyoxindoles and the subsequent transesterifications afford spirocyclic δ-lactones.

Chiral bicyclic guanidine catalyzes the asymmetric H-D exchange reactions. Up to 30% ee was achieved. DFT calculations were employed to elucidate and explain the origin of the reaction's stereoselectivity.

Asymmetric aldol reactions of α-amino acid derivatives via memory of chirality were developed. Chiral oxazolidones with contiguous tetra- and trisubstituted chiral centers were obtained in 78-94% ee by the asymmetric aldol reaction followed by intramolecular acylation.

The palladium-catalyzed Heck-Matsuda reaction with a catalytic amount of an in-situ-generated diazonium salt proceeded under mild and sustainable conditions. The reaction proceeded at room temperature, under base-free conditions, and only generated tBuOH, H(2) O, and N(2) as by-products. Ortho-substituted diazonium salts were more-efficiently coupled to methyl acrylate than their corresponding ...

The present study employs neglect dyslexia (ND) as an experimental model to study compound-word processing; in particular, it investigates whether compound constituents are hierarchically organized at mental level and addresses the possibility of whole-word representation. Seven Italian-speaking patients suffering from ND participated in a word naming task. Both left-headed (pescespada, ...

Organosilicon-mediated, regioselective acetylation of vicinal- and 1,3-diols is presented. Methyl trimethoxysilane or dimethyl dimethoxysilane was first used to form cyclic 1,3,2-dioxasilolane or 1,3,2-dioxasilinane intermediates, and subsequent acetate-catalyzed monoacylation was efficiently performed by addition of acetic anhydride or acetyl chloride under mild conditions. The reaction exhibited high regioselectivity, resulting in the ...

A series of benzopyrano[3,4-b](N-arylsulfonyl) indole derivatives and benzopyrano[4,3-b](N-arylsulfonyl) indole derivatives were synthesized from 2- or 3-methylindole via intermolecular S( N )2 reaction and subsequent intramolecular palladium-catalyzed aryl-aryl coupling reaction for the first time. It was suggested that, besides using the Fischer cyclization, benzopyrano[4,3-b]indoles and benzopyrano[3,4-b]indoles could also be prepared via ...

Finely-tuned ruthenium-catalyzed highly chemoselective and enantioselective hydrogenation of γ-halo-γ,δ-unsaturated-β-keto esters at the carbonyl group was achieved under neutral reaction conditions (ee up to 97%). Both olefin and alkenyl halogen moieties, which are labile under hydrogenation conditions, remained untouched during the reaction.

Wrap it up! An intramolecular Pd-catalyzed tandem-domino process leading to highly sterically encumbered biphenyls is reported. The chirality of the newly formed axis is induced by the configuration of the carbohydrate backbone.

Reaction of cellular thiols with the 1,2-dithiolan-3-one 1-oxide moiety of leinamycin triggers the generation of DNA-damaging reactive intermediates. Studies with small, synthetic analogues of leinamycin reveal that the macrocyclic portion of the natural product imparts remarkable hydrolytic stability to the 1,2-dithiolan-3-one 1-oxide heterocycle without substantially compromising its thiol-sensing property.

The behaviour of thioamides under Kulinkovich-type conditions is compared with the known reactivity of carboxylic amides. Dramatic differences are disclosed.

A biomimetic strategy for the synthesis of the antimalarial flindersial alkaloids is described. Flinderoles A, B, and C, desmethylflinderole C, isoborreverine, and dimethylisoborreverine were all synthesized in three steps from tryptamine. The key step is an acid-promoted dimerization of the natural product borrerine. This approach is thought to mirror the ...

In depth mechanistic studies of iridium catalyzed regioselective and enantioselective allylic substitution reactions are presented. A series of cyclometallated allyliridium complexes that are kinetically and chemically competent to be intermediates in the allylic substitution reactions was prepared and characterized by 1D and 2D NMR spectroscopies and solid state structural analysis. ...

We disclose an organocatalyzed enantioselective decarboxylative ketone aldol reaction of β-ketoacids with trifluoromethyl ketones in the presence of biscinchona alkaloid (DHQD)(2)AQN, affording chiral tertiary alcohols in up to 98% yield and 90% ee.

We have discovered a novel PdCl(2)-FeCl(2) catalyzed cascade cyclization reaction, which involves a novel acyl rearrangement process. This reaction affords a diverse set of poly-substituted 4H-cyclopenta[c]furan products. The reaction scope of this cascade process is quite broad and various internal acetylenes can be employed.

Ni-containing methyl-coenzyme M reductase (MCR) is capable of catalyzing methane formation and has recently been observed to also be able to catalyze the reverse reaction, the anaerobic oxidation of methane. The forward reaction has been extensively studied theoretically before and was found to consist of two steps. The first step ...

A homo-Michael addition reaction of lithium selenolates with 1-(1-alkynyl)cyclopropyl ketones and the subsequent reaction with electrophiles such as PhSeBr, NFSI and NCS is reported. Based on the nature of electrophiles, this reaction may afford highly substituted 1,2-allenyl ketones or furans (E(+) = PhSe(+)) and 2-alkynyl ketones (E(+) = F(+), Cl(+), ...

We report the synthesis of a variety of diamidocyclopropenes by combining an isolable and readily accessible N,N'-diamidocarbene (DAC) with a range of alkynes (nine examples, 68-97% yield). Subsequent hydrolysis of selected cyclopropenes afforded the corresponding cyclopropenones or α,β-unsaturated acids, depending on the reaction conditions. In addition, the combination of a ...

The unprecedented homolytic opening of ozonides promoted and catalyzed by titanocene(III) is reported. This novel reaction proceeds at room temperature under neutral, mild conditions compatible with many functional groups and provides carbon radicals suitable to form C-C bonds via both homocoupling and cross-coupling processes. The procedure has been advantageously exploited ...

A novel palladium-catalyzed domino reaction of 1-bromo-2-(cyclopropylidenemethyl)benzene and 2-alkynylbenzenamine is reported, which generates 2-(naphthalen-2-yl)benzenamines and 5H-indeno[1,2-c]quinolines via 6-endo and 5-exo cyclization, respectively. The regioselectivity for the final outcome can be affected by phosphine and N-heterocyclic carbene ligands.

The direct aldol reaction of an α-alkyl-α-oxo aldehyde was catalyzed by trifluoromethyl-substituted diarylprolinol 1 to afford a γ-oxo-β-hydroxy-α-substituted aldehyde in good yield with excellent anti-selectivity and excellent enantioselectivity.

A study of the aldol reactions of boron enolates from methylketones that are protected with dimethylacetonide or di-tert-butylsilyl (DTBS) groups and that possess a trans or cis relationship between the chiral centers is presented. The main objective of this work was to evaluate the influence of the relative stereochemistry between ...

The N-tosylcarboxamide group offers the possibility of directing the Pd-catalyzed C-H arylation of arenes providing a new entry to biarylcarboxamides. Moreover, its ability to react according to different reaction conditions including intramolecular reactions makes it a pivotal directing group for a divergent synthesis of biaryl-based compounds.

Enantioselective calcium-catalyzed addition reactions of styrene and indole derivatives with trifluoropyruvates have been developed. The alkaline-earth metal-catalyzed reactions proceed smoothly to afford the corresponding products in high yields and with good to excellent enantioselectivities under mild reaction conditions.

2,4,5-Triphenylimidazole (lophine) is known as the first chemiluminescence substrate, and its oxidized derivative, the 2,4,5-triphenylimidazolyl radical, corresponds to the coloured species in the photochromic reaction of hexaarylbiimidazole (HABI). We report the first direct observation of the O(2) adduct of the imidazolyl radical that forms the end-on peroxide-bridged imidazole dimer. The ...

Reported here are details on the discovery of a phosphine catalyzed isomerization of hemiketals and subsequent reactions of the cyclic keto enol ether products. The new cycloisomerization complements a previously reported amine catalyzed process that gave oxepinones from the same hemiketal starting materials. In the absence of functionality (R2) on ...

In(OTf)(3) is reported as the first catalyst having the ability to selectively catalyse both Markovnikov and anti-Markovnikov hydrothiolation of terminal alkynes under identical reaction conditions depending upon the nature of the thiol employed.

The 1H-indazole skeleton can be constructed by a [3 + 2] annulation approach from arynes and hydrazones. Under different reaction conditions, both N-tosylhydrazones and simple N-aryl/alkylhydrazones can be used to afford a variety of indazoles. The former reaction affords 3-substituted indazoles either via in situ generated diazo compounds or through ...

A palladium-catalyzed three-component reaction of bis-(2-iodoaryl)carbodiimide, isocyanide, and amine gives rise to quinazolino[3,2-a]quinazolines and related compounds in good yields. Multi-bonds are formed in one pot through nucleophilic attack, isocyanide insertion, and C-N coupling during the reaction process.

A practical and chromatography-free synthesis of vinamidinium salts and their use as diene precursors in Diels-Alder reactions is reported. Additionally, 1,3-dipyrrolidino-1,3-butadiene was shown to be significantly more reactive than Rawal's diene in a competition experiment.

Highly enantioselective synthesis of chiral chromenes and tetrahydroquinolines is achieved by combining asymmetric copper-catalyzed allylic substitution with Grignard reagents and an efficient intramolecular Heck reaction. Moreover, the exocyclic double bond formed in the cyclisation was subjected to RCM, hydroboration and hydrogenation illuminating the synthetic versatility of these heterocycles.

A general approach to asymmetric synthesis of highly substituted spirodihydrocoumarins with a quaternary stereocenter was achieved through neighboring ortho-hydroxyl group induced sequential Michael-lactonization reactions on 2-(2-nitrovinyl)phenols with alkyl cyclopentanone-2-carboxylates in the presence of a catalytic amount of quinine-NH-thiourea followed by p-TSA.

An unprecedented nickel-catalysed disproportional reaction of 2,3-diaryl-2H-azirines forming azabutadienes and aromatic nitriles was discovered. This reaction involves the cleavage of two bonds of the 2H-azirine framework, which provides a novel type of transformation of 2H-azirines.

A novel route for the efficient assembly of indeno[1,2-c]pyrrole derivatives via a palladium-catalyzed tandem reaction of 2-alkynylbromobenzene with propargylic sulfonamide is reported. The starting materials are easily available, and the reaction proceeds smoothly with good functional group tolerance.

A novel asymmetric formal [3 + 2] cycloaddition reaction for the synthesis of 1,3-dioxolanes using cinchona-alkaloid-thiourea-based bifunctional organocatalysts is reported. The reaction proceeds via the formation of hemiacetal intermediates between γ-hydroxy-α,β-unsaturated ketones and aldehydes.

Rh(I)/diene-catalyzed addition reactions of arylboroxines/arylboronic acids with unactivated ketones to form tertiary alcohols in good to excellent yields are described. By using C(2)-symmetric (3aR,6aR)-3,6-diaryl-1,3a,4,6a-tetrahydropentalenes as ligands, the asymmetric version of such an addition reaction, with up to 68% ee, was also realized.

In this study, we report the synthesis of several novel dihydroisoxazole-, tetrahydroisoxazole- and dihydropyrazole-fused pyrido[2,3-b]quinolines, α-carbolines, and pyrido[2,3-c]coumarins, respectively, from simple precursors and by exploring intramolecular 1,3-dipolar cycloaddition reactions involving nitrile oxides, nitrones, and nitrile imines as 1,3-dipoles.

An application of the classical Ritter reaction for the synthesis of unsymmetrical di and trisubstituted ureas catalyzed by FeCl(3) is described. The protocol is of significant interest in view of the easy availability of precursors, mild reaction conditions employed and interestingly its applicability for the alkylation of alcohols capable of ...

The first stereoselective synthesis of (Z)-cryptomoscatone D2, a naturally occurring G(2) checkpoint inhibitor, was accomplished using propane-1,3-diol as the starting material. The Maruoka asymmetric allylation, ring closing metathesis and the hydrogenation of the triple bond employing Lindlar's catalyst were involved as the key steps.

A variety of substituted benzisoxazolines have been synthesized by the [3 + 2] cycloaddition of nitrones and arynes. The reaction scope is broad, the reaction conditions are mild, and the process tolerates a variety of functional groups.

The reactions of the chalcogen halides (Ch = S, Se, Te) with a series of diiminopyridine (DIMPY) ligands were explored. It was determined through these studies that varying both the substitution on the α-carbon and the chalcogen halide reagent afforded different products. If methyl groups were present on the α-carbon, ...

A new Rh-catalyzed intramolecular coupling reaction of a CF(2)Br group with a 2-aryl of indole or pyrrole via C-H bond activation is presented. This reaction represents a new way of incorporating difluoromethylene groups into organic compounds. Preliminary mechanistic studies suggest that this reaction might not occur via a conventional free ...

Stereoselective syntheses of both functionalized tetrahydropyran subunits of (-)-lasonolide A are described. These tetrahydropyran rings were constructed using catalytic asymmetric hetero Diels-Alder reactions as the key steps. The C22 quaternary stereocenter present in the upper tetrahydropyran ring was constructed by a stereoselective alkylation, and the C9 hydroxy stereochemistry of the ...

Exchanging BF(3) by CF(3) : The title reaction proceeds under exceedingly mild reaction conditions and provides 2-arylvinyl- and 2-heteroarylvinyl-substituted substrates with E/Z selectivities of more than 95:5. Experimental observations suggest that the reaction does not proceed through a transmetalation of the RBF(3) K species to the iron catalyst.