Regioselective hydroaminomethylation of 1,1-diaryl-allyl-alcohols: a new access to 4,4-diarylbutylamines

Pharmacologically active 4,4-diarylbutylamines like Fluspirilene and 4-amino-1,1-diarylbutan-1-ols like Difenidol were prepared in high yields via rhodium catalysed hydroaminomethylation of 1,1-diaryl-allylalcohols. Conversion of these olefins with carbon monoxide, hydrogen and secondary amines proceeds with complete regioselectivity. This group can easily be removed under acidic and hydrogenating conditions, enabling the transformation of 4-amino-1,1-diarylbutan-1-ols to 4,4-diarylbutylamines in high yields. Thus Fluspirilene was synthesised in 88% yield in four steps starting from commercially available materials.     

An improved protocol for the selective hydroaminomethylation of arylethylenes

The hydroaminomethylation of arylethylenes with anilines proceeds under mild conditions in the presence of [Rh(cod)₂BF₄] and dppf as catalyst system to give the corresponding branched amphetamine derivatives in good selectivity and yield.     

Behaviour of water-soluble dinuclear rhodium complexes in the hydroformylation reaction of oct-1-ene

The biphasic hydroformylation reaction of oct-1-ene, has been investigated by using the water-soluble dinuclear complex [Rh₂(μ-S^tBu)₂(CO)₂(TPPTS)₂] as precursor. Addition of ethanol as a cosolvent dramatically improved the yields but the good regioselectivity in linear aldehyde observed for neat oct-1-ene—water systems (97%) decreased to 83% (for 22% ethanol w/w). It is shown that the dinuclear framework cannot be maintained, that the mononuclear complex [RhH(CO)(TPPTS)₃] is formed, and that thiol and significant amounts of [Rh₂(μ-S^tBu)₂(CO)₄] move into the organic phase. This reaction from the dinuclear species requires the simultaneous presence of water and carbon monoxide. Introduction of the water-soluble thiol HS(CH₂)₃NMe₂ in the bridging positions affords the complex [Rh₂(μ-S(CH ₂)₃NHMe₂)₂(CO)₂(TPPTS)₂]Cl₂ which can be kept in the aqueous hase but has a low level of catalytic activity.     

Isomerisation of ω-hydroxyalkenes under hydroxycarbonylation conditions in palladium catalysed aqueous phase systems

The ω-hydroxyolefins 3-buten-1-ol, 3-buten-1-methyl-1-ol and 4-penten-1-ol were subjected to hydroxycarbonylation conditions in water in the presence of PdCl₂(PhCN)₂ and 4-8 equiv. of water soluble tris(3-sodiumsulfonatophenyl)phosphine (TPPTS), or N-bis(N′,N′-diethyl-2-aminoethyl)-4-aminomethylphenyl-diphenylphosphine (N3P). Under conditions of high conversion, the olefins primarily undergo isomerisation through a chain walking mechanism with selectivities for aldehyde ranging from 65% to 98%, with the lower values for longer chain alcohols. The lactones formed as the minor product are almost exclusively branched, indicating that in the first step 2,1-insertion is strongly favoured over 1,2-insertion. In the N3P system also linear lactone is produced at lower conversion. Running the reaction in D₂O produces multiple deuterium incorporation in all positions of the carbon chain. A mechanism is discussed.     

Rhodium-catalyzed intramolecular hydroacylation of 1,2-disubstituted alkenes for the synthesis of 2-substituted indanones

The intramolecular hydroacylation of 1,2-disubstituted alkenes was considered to be a challenging task due to the side reactions resulted from the lack of additional substituent at 1-position and the low activity caused by the steric hindrance of substituent at 2-position, and an asymmetric version has not been considered possible due to problems associated with the racemization of the products. We have partially solved these problems. Catalyzed by an activated diphosphine-Rh complex and reacted in a selected dihalogenated solvent, the intramolecular hydroacylation of o-(2-arylvinyl)benzaldehydes provided the corresponding 2-aryl-1-indanones in high yields, and its asymmetric variant using o-(2-alkylvinyl)benzaldehydes afforded chiral 2-alkyl-1-indanones in high yields and with moderate enantioselectivities.     

First iron-catalyzed guanylation of amines: a simple and highly efficient protocol to guanidines

The first iron-catalyzed guanylation of amines is reported. Commercially available Fe(OAc)₂ acts as an excellent catalyst for the addition of amines to carbodiimides. The reaction is broadly applicable to a variety of primary, secondary, and heterocyclic amines, and tolerates a wide range of functionalities allowing the easy preparation of a large family of guanidines. The low price and low toxicity of the commercially available iron catalyst make this methodology highly attractive.     

Rh nanoparticles stabilized by PEG-substituted triphenyl-phosphine:A highly active and recyclable catalyst for aqueous biphasic hydrogenation of benzene

<正>Rh nanoparticles stabilized by PEG-substituted triphenyl-phosphine(PETPP,P[C_6H_4-p-(OCH_2CH_2)_nOH]_3) combining double stabilization effects demonstrated high activity and good recyclability in aqueous biphasic hydrogenation of benzene.The value of turnover frequency(TOF) was 3333 h~(-1).Furthermore,the rhodium nanoparticle catalyst could be easily recycled for five times without loss in activity.     

Rh-catalyzed addition of boronic acids to alkynes for the synthesis of trisubstituted alkenes in a biphasic system - Mechanistic study and recycling of the Rh/m-TPPTC catalyst

The versatile preparation of trisubstituted alkenes via selective Rh-catalyzed arylation of alkynes is described in water and in a water/toluene biphasic system. For hydrophobic alkyl alkynes, the reaction afforded either alkenes or dienes depending on the temperature and the solvent conditions. Aryl, heteroaryl, silylated and alkyl substituted alkynes reacted equally well with various boronic acids, leading regioselectively to functionalized alkenyl derivatives in high yields (65-99%). The mechanism was investigated in toluene/water mixture or water and involves a vinylrhodium complex. The efficient recycling of the Rh/m-TPPTC system is disclosed with excellent yield (92-96%) and purity of the alkene.     

Synthesis of novel rhodium phosphite catalysts for efficient and selective isomerization-hydroformylation reactions

New modular H₈-BINOL-based phosphite ligands have been synthesized. High activity and regioselectivity has been achieved in the rhodium-catalyzed isomerization-hydroformylation of internal olefins. The active catalysts have been characterized by insitu NMR studies.     

A Novel Class of Ruthenium Catalysts for Olefin Metathesis

The different nature of carbene ligands is clearly demonstrated by the first ruthenium-based complexes 1 , which contain both alkylidene and N-heterocyclic carbene moieties. The latter exhibit a pronounced Lewis base behavior. Moreover, this difference forms the basis of the high catalytic activities of these compounds in olefin metathesis reactions.     

ZrOCl2·8H2O in water: An efficient catalyst for rapid one-pot synthesis of pyridopyrazines,pyrazines and 2,3-disubstituted quinoxalines

Zirconium(IV) oxide chloride was found to be a rapid and efficient catalyst for the synthesis of pyrazines and 2,3-disubstituted quinoxalines in water. A variety of pyridopyrazine and 2,3-disubstituted quinoxaline derivatives are readily prepared in high yields under green conditions by cyclocondensation of the desired 1,2-diamine and 1,2-diketone using a catalytic amount of zirconium(IV) oxide chloride in water. Less active diamines, such as 2,3- and 3,4-diaminopyridines took part in this protocol to provide the desired products in good to excellent yields.     

Fluorous biphasic catalysis with dirhodium(II) perfluorocarboxylates: selective silylation of alcohols under fluorous biphasic conditions

Dirhodium(II) perfluorocarboxylates bearing C7–C13 perfluoroalkyl chains have been prepared and used as catalysts under fluorous biphasic conditions. They were found to be active and recyclable catalysts for the silylation of alcohols with triethylsilane. Hydrophobic, primary alcohols are preferentially silylated by the fluorous biphasic catalytic system in comparison with hydrophilic or secondary ones. This opens the way to the development of selective silylation protocols.     

A novel method for the reduction of alkenes using the system silane/oxo-rhenium complexes

In this work, we report the first practical application of high-valent oxo-complexes for the reduction of alkenes to the corresponding alkanes. The catalytic system Ph(Me)₂SiH/ReIO₂(PPh₃)₂ (5 mol %) proved to be very efficient for the reduction of mono- and disubstituted alkenes under solvent-free conditions.     

The first use of porphyrins as catalysts in cross-coupling reactions: a water-soluble palladium complex with a porphyrin ligand as an efficient catalyst precursor for the Suzuki-Miyaura reaction in aqueous media under aerobic conditions

For the first time, a palladium complex with a porphyrin ligand is used as a catalyst precursor for cross-coupling reactions. The synthesis of a palladium complex with a phosphine-free and water-soluble potassium carboxylate salt of a porphyrin, and its evaluation in the Suzuki-Miyaura reaction of phenylboronic acid with aryl bromides (from electron-rich to electron-poor), in neat water, under aerobic conditions is described. Catalysis is performed at 100 °C for 4 h, using K₂CO₃ as base, and a substrate to catalyst molar ratio of 1000:1, leading to yields of coupling products in the range of 80-100%. The catalyst can be recycled and reused, but unfortunately, with a loss in activity.     

Zinc oxide (ZnO) as a new, highly efficient, and reusable catalyst for acylation of alcohols, phenols and amines under solvent free conditions

Zinc oxide (ZnO) is a highly efficient catalyst for the acylation of a variety of alcohols, phenols and amines with acid chlorides or acid anhydrides under solvent free conditions. Primary, secondary, tertiary, allylic and benzylic alcohols, diols and phenols with electron donating or withdrawing substituents can be easily acylated in good to excellent yield.     

Rhodium(I)-Catalyzed [2+2+2] Cycloadditions with N-Functionalized 1-Alkynylamides: A Conceptually New Strategy for the Regiospecific Synthesis of Substituted Indolines

The regiospecific introduction of substituents into the 4-position of 2,3-dihydroindoles (indolines), which is significant for the synthesis of various natural products and pharmaceuticals, was achieved by rhodium(I )-catalyzed cyclotrimerizations of 1 with acetylene to give 2 . Up to four substituents can be introduced simultaneously into the indoline core by using this novel strategy. R=OH, OBzl, Otetrahydropyranyl, NHSO₂C₆H₄CH₃; Ts=H₃CC₆H₄SO₂.     

A mild and efficient method for the reduction of nitriles

A simple and useful method for the reduction of nitriles into the corresponding amines using a tetramethyldisiloxane/titanium(IV) isopropoxide reducing system is described. The synthetic approach is straightforward and provides primary amines as hydrochloride salt in almost quantitative yield. Other advantages of this method, such as easy-to-handle hydride source, inert by-products, that is, TiO₂ and oligomeric siloxanes, make it very attractive to prepare primary amines.     

Molecular iodine in isopropenyl acetate (IPA): a highly efficient catalyst for the acetylation of alcohols, amines and phenols under solvent free conditions

Iodine in isopropenyl acetate (IPA) is a highly efficient catalyst for the acetylation of a variety of alcohols, phenols and amines under solvent free conditions. Primary, secondary, tertiary alcohols, amines and mono to polyhydroxy phenols and anilines with electron donating or withdrawing substituents can be easily acetylated in good to excellent yield at 85-90 °C.     

A three-component reaction between alkenes, secondary phosphanes, and elemental selenium: a novel, efficient, atom-economic synthesis of diselenophosphinic esters

A novel, convenient, atom-economic approach toward the synthesis of diselenophosphinic esters has been developed via the three-component reaction between aryl- or hetarylalkenes secondary phosphanes, and elemental selenium. The reaction proceeds without a catalyst (85 °C, 3 h, 1,4-dioxane) to afford the target compounds in good to high yields.