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.     

A one-pot process for the enantioselective synthesis of amines via reductive amination under transfer hydrogenation conditions

[reaction: see text]. Cyclic amines may be prepared via a sequence of deprotection followed by intramolecular reductive amination of t-Boc-protected amino ketones under asymmetric transfer hydrogenation conditions. In cases where the corresponding imine reaction proceeds with high enantioselectivity, this is reflected in the one-step process.     

Multicomponent one-pot procedure for the synthesis of free alpha-chiral amines from aldehydes

[reaction: see text] The synthesis of free alpha-chiral amines by a one-pot multicomponent procedure from commercially available starting materials is described. This enantioselective reaction involves a catalytic asymmetric addition of dialkylzinc reagents to N-diphenylphosphinoylimines with use of an air-stable precatalyst complex 1. The alpha-chiral amines are prepared with a one-pot procedure from alkyl and aryl aldehydes in good yield (41-90%) and with excellent enantioselectivity (90-97% ee).     

Selective synthesis of secondary amines by Pt nanowire catalyzed reductive amination of aldehydes and ketones with ammonia

The process of the reductive amination of aldehydes or ketones in the presence of ammonia using unsupported ultra-thin Pt nanowires has been developed. This catalytic system shows high activity and selectivity under mild reaction conditions.     

Direct reductive amination of carbonyl compounds with primary/secondary amines using recyclable water-soluble Fe/EDTA complex as catalyst

Direct reductive amination of aliphatic, aromatic and heterocyclic carbonyl compounds with primary/secondary amines is reported with water-soluble Fe^II/EDTA complex as a catalyst using low-pressure molecular hydrogen in a biphasic media. The catalyst is highly selective, recyclable and is an excellent replacement for expensive noble metal catalysts or stoichiometric reducing agents.     

Direct reductive amination of aldehydes and ketones using phenylsilane: catalysis by dibutyltin dichloride

A procedure for direct reductive amination of aldehydes and ketones was developed which uses phenylsilane as a stoichiometric reductant and dibutyltin dichloride as a catalyst. Suitable amines included anilines and dialkylamines but not monoalkylamines.     

A novel one-pot reductive amination of aldehydes and ketones with lithium perchlorate and zirconium borohydride-piperazine complexes

A novel, one-pot reductive mono-alkylation method of amines (primary and secondary), 1,2-phenylenediamine, O-trimethylsilylhydroxylamine, and N,N-dimethylhydrazine was developed using LiClO₄ (5 mol %) as a source for in situ generation of imine, iminium ion, oxime, and hydrazone, and zirconium borohydride-piperazine complex as reducing agent. This condition is especially useful for situations in which it is not practical to use the amine in excess (as is typically the case under acid-catalyzed conditions) or for acid-sensitive compounds.     

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.     

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.     

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.     

A one-pot, reductive amination/6-endo-trig cyclisation for the stereoselective synthesis of 6-substituted-4-oxopipecolic acids

The first stereoselective synthesis of 2,6-trans-6-substituted-4-oxo-L-pipecolic acids using a tandem reductive amination/6-endo-trig cyclisation process is described. The sequential reduction and cyclisation mediated by sodium cyanoborohydride allowed the preparation of a series of highly functionalised 6-alkyl and 6-aryl analogues.     

Direct reductive amination of aromatic aldehydes catalyzed by gold(I) complex under transfer hydrogenation conditions

The direct reductive amination of aromatic aldehydes has been achieved with excellent isolated yields (89-96%) using readily accessible Ph(3)PAuCl/AgOTf catalyst along with ethyl Hantzsch ester as hydrogen source under mild reaction conditions.     

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 simple and convenient procedure for the synthesis of 1-aminophosphonates from aromatic aldehydes

A simple, efficient, possible industrial process has been developed for the synthesis of 1-aminophosphonic acids from simple starting materials. As described below, treatment of aromatic aldehydes with ammonia and reaction with diethyl phosphite gives diethyl N-(arylmethylene)-1-aminoaryl methylphosphonates, which can be easily hydrolyzed to diethyl 1-aminoarylmethylphosphonates. This method is easy, rapid, and good yielding for the synthesis of 1-aminoalkylphosphonates from simple starting materials.     

A convenient one-pot procedure for synthesis of thiol esters using magnesium ion as a catalyst

Various thiol esters (R¹ COSR²) were prepared in high yields by treatment of 1-acylimidazole with thiols in the presence of a catalytic amount of Mg(OEt)₂. Malonic half-thiol esters [R¹OCOCH(R³)COSR²] were also prepared in good yields by treating magnesium monoalkyl malonate [R¹ OCOCH(R³)COOMg$\text{1}\text{2}$] with carbonyl-1,1′-diimidazole followed by addition of thiols.     

A simple one-pot procedure for the direct conversion of alcohols into azides using TsIm

A facile and efficient method for one-pot conversion of alcohols into azides using N-(p-toluenesulfonyl)imidazole (TsIm) is described. In this method, alcohols are refluxed with a mixture of NaN₃, TsIm and triethylamine in the presence of catalytic amounts of tetra-n-butylammonium iodide (TBAI) in DMF affording the corresponding alkyl azides in good yields. This methodology is highly efficient for various structurally diverse alcohols with selectivity for ROH: 1° > 2° > 3°.     

The direct reductive amination of electron-deficient amines with aldehydes: the unique reactivity of the Re2O7 catalyst

An unprecedented direct reductive amination of electron-deficient amines such as Cbz-, Boc-, EtOCO-, Fmoc-, Bz-, ArSO(2)-, Ar(2)PO-, etc. protected amines with aldehydes is achieved using the Re(2)O(7) catalyst and silanes as the hydride source. Excellent regioselective mono-alkylation and chemoselective reductive-amination were observed.     

A simple and efficient procedure for the synthesis of benzimidazoles using air as the oxidant

Direct one-step synthesis of various benzimidazoles from phenylenediamines and aldehydes is described using air as the oxidant. The salient features of this method include a simple procedure, mild conditions, no coupling agents or commercial oxidants/additives used, no waste produced (only by-product being water), easy purification, and high generality.     

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.     

A highly stereoselective reductive amination of 3-ketosteroid with amines: an improved synthesis of 3α-aminosteroid

A highly stereoselective reductive amination method was developed based on in situ generated sodium acyloxyborohydride and was successfully applied to a steroidal skeleton with various amine sources. High yield (96%) and a de of up to 95% were achieved by modifying the reducing reagent. The effect of this reagent will be discussed.