An efficient,recoverable fluorous organocatalyst for accelerating the DABCO-promoted Morita-Baylis-Hillman reaction

A convenient method for Morita-Baylis-Hillman reaction of arylaldehydes with methyl acrylate has been developed by using fluorous-tag organocatalyst 1-[4-(perfluorooctyl)phenyl]-3-phenylthiourea and DABCO at room temperature.The fiuorous, organocatalyst could be recovered from the reaction mixture by fiuorous solid-phase extraction(F-SPE) with excellent purity for direct reuse.     

S-Benzyl isothiouronium chloride as a recoverable organocatalyst for the direct reductive amination of aldehydes

The direct reductive amination of aldehydes using S-benzyl isothiouronium chloride as a recoverable organocatalyst for the activation of the imine intermediate through hydrogen bonding is described. A mild and operationally simple fragment coupling procedure was accomplished with a wide range of aldehydes as well as amines in good to excellent yields. In addition, the S-benzyl isothiouronium chloride catalyst was easily recovered by simple filtration and reused without any drop in its efficiency.     

A recyclable fluorous thiourea organocatalyst for the chemoselective oxidation of sulfides

As a kind of organocatalyst, 1-[4-(perfluorooctyl)phenyl]-3-phenylthiourea was employed to the chemoselective oxidation of sulfides in the presence of 30% H₂O₂. A variety of diaryl, dialkyl, alkyl aryl sulfides could be oxidized to sulfoxide under the mild condition. The catalyst could be easily recovered by fluorous solid-phase extraction for reuse.     

Asymmetric Michael additions of aldehydes to maleimides using a recyclable fluorous thiourea organocatalyst

Fluorous thiourea organocatalyst 3 promotes the Michael reaction of aldehydes with maleimides to afford the corresponding adducts in high yields with up to 99% ee. Fluorous organocatalyst 3 can be easily recovered as an insoluble precipitate from the reaction mixture by simple filtration and can be reused without significant loss of catalytic activity.     

Iron triflate catalyzed reductive amination of aldehydes using sodium borohydride

An efficient and convenient procedure for the reductive amination of aldehydes using NaBH₄ in the presence of catalytic amount of Fe(OTf)₃ is described.     

ZrCl4/Hantzsch 1,4-dihydropyridine as a new and efficient reagent combination for the direct reductive amination of aldehydes and ketones with weakly basic amines

ZrCl4/Hantzsch 1,4-dihydropyridine is a mild and highly efficient reagent combination for the direct reductive amination.Weakly basic amines such as anilines substituted by electron-withdrawing group and heteroaromatic amines can be reductivelyalkylated with electron rich aldehydes and ketones under mild conditions to form the secondary amines in excellent yields.     

One-pot reductive amination of aldehydes catalyzed by a hydrio-iridium(III) complex in aqueous medium

A combination of sodium tetrakis[3,5-di(trifluoromethyl)phenyl]borate [NaBAr^F₄] and hydrio-iridium(III) complex efficiently catalyzed the one-pot reductive amination of aldehydes with various amines and ammonia in water under mild conditions in good to excellent yields.     

An efficient and recoverable palladium organocatalyst for Suzuki reaction in aqueous media

Meso‐tetrakis[4‐(methoxycarbonyl)phenyl]porphyrinatopalladium(II) as a palladium organocatalyst was synthesized and then used in aqueous media as a heterogeneous organocatalyst in Suzuki reaction. The prepared organocatalyst was characterized using UV–visible, infrared and NMR spectroscopies. It was found to be an efficient catalyst for Suzuki coupling reaction between phenylboronic acid and a broad range of aryl halides. Mild reaction conditions, water solvent as green media, and easy catalyst separation and reusability are the advantages of the presented method.     

One-pot reductive amination of aldehydes and ketones with α-picoline-borane in methanol, in water, and in neat conditions

A one-pot reductive amination of aldehydes and ketones with amines using α-picoline-borane as a reducing agent is described. The reaction has been carried out in MeOH, in H₂O, and in neat conditions in the presence of small amounts of AcOH. This is a highly efficient and mild procedure that is applicable for a wide variety of substrates. In particular, this is the first successful demonstration that this type of reaction can be carried out in water and in neat conditions.     

First example of direct reductive amination of aldehydes with primary and secondary amines catalyzed by water-soluble transition metal catalysts

An unprecedented efficient and highly selective direct reductive amination of aldehydes with primary and secondary amines in water using gaseous hydrogen and water-soluble catalysts is developed. The catalytic system formed in situ from Pd(PhCN)₂Cl₂ and 2,2′-biquinoline-4,4′-dicarboxylic acid dipotassium salt (BQC), allows full conversion of aldehydes and the formation of desired alkylated amines with excellent yields and selectivities. The catalytic system is stable and can be recycled and reused three times without loss of activity.     

Direct and indirect reductive amination of aldehydes and ketones with solid acid-activated sodium borohydride under solvent-free conditions

A simple and convenient procedure for reductive amination of aldehydes and ketones using sodium borohydride activated by boric acid, p-toluenesulfonic acid monohydrate or benzoic acid as reducing agent under solvent-free conditions is described.     

Direct reductive amination of carbonyl compounds using bis(triphenylphosphine) copper(I) tetrahydroborate

A direct reductive amination protocol for aldehydes/ketones using bis(triphenylphosphine) copper(I) tetrahydroborate as a novel reducing agent in the presence of sulfamic acid has been developed. The reagent chemoselectively reduces the imine moiety and does not affect other reducible functionalities such as chloro, nitro, cyano and methoxy.     

Direct Leuckart-type reductive amination of aldehydes and ketones: a facile one-pot protocol for the preparation of secondary and tertiary amines

A high-yielding and facile one-pot Leuckart-type reaction for rapid access to a number of 2° and 3° amines is described.     

Microwave-accelerated methodology for the direct reductive amination of aldehydes

[chemical reaction: see text]. An improved procedure for the direct reductive amination of aldehydes was developed which uses dibutyltin dichloride as catalyst in the presence of phenylsilane as reductant. Rapid reaction is promoted by the use of microwave conditions with anilines, secondary and primary amines being suitable reactants.     

Synthesis,characterization, and application of silica supported ionic liquid as catalyst for reductive amination of cyclohexanone with formic acid and triethyl amine as hydrogen source

A silica supported ionic liquid was synthesized and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, X-ray diffraction, N2 adsorption-desorption, and thermogravimetric analysis. All these techniques, especially SEM results indicated the presence of well-defined spherical particles having diameters larger than the pristine silica particles, confirming the successful immobilization of the ionic liquid. The prepared silica supported ionic liquid was used in the reductive amination of cyclohexanone under different conditions with different azeo-tropic mixtures of formic acid and triethyl amine as a hydrogen source. The catalyst showed effi-cient catalytic performance and excellent yields of N-cyclohexyl amine derivatives in the range of 58%to 84%at 30 °C. After completion of the reaction, the catalyst was easily recovered by simple filtration and reused for another five cycles without any significant impact on product yields. The obtained catalytic performance indicates that the present catalyst is green, very active, and reusable for the reductive amination of cyclohexanone.     

A practical fluorous benzylidene acetal protecting group for a quick synthesis of disaccharides

A new fluorous benzylidene acetal protecting group was regioselectively introduced into carbohydrates, deprotected under acidic conditions, and reused. Oligosaccharides were synthesized via regioselective conversion of the fluorous acetal group to the benzyl group by traditional reaction conditions. The fluorous compounds were easily separated from non-fluorous by-products by fluorous solid phase extraction.     

A selective reductive amination of aldehydes by the use of Hantzsch dihydropyridines as reductant

Direct reductive amination of an aldehyde was carried out using a Hantzsch dihydropyridine as the reductant in the presence of a catalytic amount of scandium triflate. The reaction was highly selective towards aldehydes over ketones, and other reducible functional groups did not affect the reaction.     

Preparation of RCM substrates for azepinoindole synthesis: reductive amination versus tetrahydro-γ-carboline formation

Treatment of N-(phenylsulfonyl)-2-vinyl-3-indolecarbaldehydes with primary aliphatic amines under mild reductive amination conditions leads to tetrahydro-γ-carbolines in high yield. The process can be suppressed by changing the protecting group at the indole nitrogen for a methoxymethyl group, thus allowing the preparation of RCM substrates for azepinoindole synthesis.     

Recyclable fluorous organocatalysts promoted three-component reactions of pyruvate,aldehyde and amine at room temperature

A new fluorous imine carbothioate has been prepared as an organocatalyst for the synthesis of pyrrol-2-ones via the cyclo-condensation reaction of aldehydes, amines, and pyruvate at room temperature. The fluorous catalyst can be easily recovered from the reaction mixture by simple fluorous solid-phase extraction (F-SPE) and used for next run reaction without further purification.     

Synthesis of hindered tertiary amines by a mild reductive amination procedure

An efficient metal-free procedure for the synthesis of tertiary amines by the reductive amination of carbonyl compounds is reported, which allows a convergent access to sterically hindered amines of the general formulas NR(R′)₂ and NRR′R″. The mild and operationally simple protocol uses the Hantzsch ester for transfer hydrogenation and catalytic amounts of thiourea for imine activation.