Microwave-Assisted Solventless Reaction of Iridium-Catalyzed Alkylation of Amines with Alcohols in the Absence of Base

Ir-Catalyzed Synthesis of Functionalized Pyrrolidines and Piperidines Using the Borrowing Hydrogen Methodology

The Ir(III)-catalyzed synthesis of 3-pyrrolidinols and 4-piperidinols combining 1,2,4-butanetriol or 1,3,5-pentanetriol with primary amines was carried out. This borrowing hydrogen methodology was further extended to the sequential diamination of triols leading to amino-pyrrolidines and amino-piperidines.

Chemoselective Reduction of Tertiary Amides by 1,3-Diphenyl­disiloxane (DPDS)

A convenient procedure for the chemoselective reduction of tertiary amides at room temperature in the presence of air and moisture using 1,3-diphenyldisiloxane (DPDS) is developed. The reaction conditions tolerate a significant number of functional groups including esters, nitriles, secondary amides, carbamates, sulfoxides, sulfones, sulfonyl fluorides, halogens, aryl-nitro groups, and arylamines. The conditions reported are the mildest to date and utilize EtOAc, a preferred solvent given its excellent safety profile and lower environmental impact. The ease of setup and broad chemoselectivity make this method attractive for organic synthesis, and the results further demonstrate the utility of DPDS as a selective reducing agent.

Trimethyl Borate-Catalyzed, Solvent-Free Reductive Amination

Solvent-free reductive amination of aldehydes and ketones with aliphatic and aromatic amines in high-to-excellent yields has been achieved with sub-stoichiometric trimethyl borate as promoter and ammonia borane as reductant.

Ruthenium Catalyzed Tandem Pictet-Spengler Reaction

We report a pyridyl-phosphine ruthenium(II) catalyzed tandem alcohol amination/Pictet-Spengler reaction sequence to synthesize tetrahydro-β-carbolines from an alcohol and tryptamine. Our conditions use a Lewis acid cocatalyst, In(OTf)₃, that is compatible with typically base catalyzed amination and an acid catalyzed Pictet-Spengler cyclization. This method proceeds well with benzylic alcohols, heterocyclic carbinols, and aliphatic alcohols. We also show how combining this reaction with a subsequent cycloamination enables a direct synthesis of tetracyclic alkaloids like harmicine.

A hydrogen borrowing annulation strategy for the stereocontrolled synthesis of saturated aza-heterocycles

A hydrogen borrowing annulation strategy enables the stereocontrolled synthesis of C2, C3 and C4-substituted saturated aza-heterocycles.

Ruthenium-catalyzed synthesis of N-substituted lactams by acceptorless dehydrogenative coupling of diols with primary amines

Herein, we report the first example of synthesis of N-substituted lactams via an acceptorless dehydrogenative coupling of diols with primary amines in one step, which was enabled by combining Ru3(CO)12 with a hybrid N-heterocyclic carbene-phosphine-phosphine ligand as the catalyst.

Nickel-catalyzed borrowing hydrogen annulations: access to diversified N-heterocycles

An efficient nickel-catalyzed synthesis of diversified N-heterocycles via atom-economic borrowing hydrogen annulations of easily available alcohols and amines.

An efficient and atom-economical route to N-aryl amino alcohols from primary amines

In this paper we reported a novel method for generation of N-aryl amino alcohols from N,N-disubstituted picolinamides through reduction/ring-opening reaction with NaBH₄. The N,N-disubstituted picolinamides can be easily obtained from primary amines after convenient condensation with picolinic acid and coupling with cyclic ethers. The whole route proceeded under simple and mild conditions with high efficiency. Picolinic acid can be recovered in the form of piconol after reaction. It indicated an efficient and atom-economical route for the preparation of N-aryl amino alcohols from primary amines.

A novel method for generation of N-aryl amino alcohols from N,N-disubstituted picolinamides through reduction/ring-opening reaction with NaBH₄ was developed.

Facile and Green Synthesis of Saturated Cyclic Amines

Single-nitrogen containing saturated cyclic amines are an important part of both natural and synthetic bioactive compounds. A number of methodologies have been developed for the synthesis of aziridines, azetidines, pyrrolidines, piperidines, azepanes and azocanes. This review highlights some facile and green synthetic routes for the synthesis of unsubstituted, multisubstituted and highly functionalized saturated cyclic amines including one-pot, microwave assisted, metal-free, solvent-free and in aqueous media.

Selective and recyclable rhodium nanocatalysts for the reductive N-alkylation of nitrobenzenes and amines with aldehydes

Heterogeneous Rh@CN nanocatalysts were prepared and applied for the reductive N-alkylation of nitrobenzenes with aldehydes selectively.

Benzimidazolin-2-ylidene N-heterocyclic carbene complexes of ruthenium as a simple catalyst for the N-alkylation of amines using alcohols and diols

Simple non-chelating ruthenium benzimidazolin-2-ylidene complexes as efficient N-alkylation catalysts using alcohols and diols following a hydrogen borrowing strategy.

An efficient heterogenized palladium catalyst for N-alkylation of amines and α-alkylation of ketones using alcohols

Silica supported palladium–NiXantphos complex is an efficient and high turnover heterogeneous catalyst for N-alkylation of amines and α-alkylation of ketones using alcohols under neat conditions at 120–140 °C following hydrogen borrowing strategy.

Simple, versatile, and chemoselective reduction of secondary amides and lactams to amines with the Tf2O–NaBH4 or Cp2ZrHCl–NaBH4 system

A convenient method for the direct reduction of secondary amides and lactams to amines is reported.

Substitution of alcohols by N-nucleophiles via transition metal-catalyzed dehydrogenation

This review summarizes the recent advances in transition metal-catalyzed dehydrogenative substitution of alcohols by N-nucleophiles since 2009.

Iron-catalyzed synthesis of secondary amines: on the way to green reductive aminations

Amines represent important intermediates in chemical and biological processes. Herein, we describe the use of a nanostructured iron-based catalyst for the tandem reductive amination between nitroarenes and aldehydes using hydrogen as reductant. The nanostructured iron-catalyst is prepared by immobilization of an iron-phenanthroline complex onto a commercially available carbon support. In the reaction sequence a primary amine is formed in situ from the corresponding nitro compound. Reversible condensation with aldehydes forms the respective imines, which are finally reduced to the desired secondary amine. This synthesis of secondary amines is atom-economical and environmentally attractive using cheap and readily available organic compounds as starting materials.

Ruthenium-catalyzed N-alkylation of amines with alcohols under mild conditions using the borrowing hydrogen methodology

Using a simple amino amide ligand, ruthenium-catalyzed one-pot alkylation of primary and secondary amines with simple alcohols was carried out under a wide range of conditions. Using the alcohol as solvent, alkylation was achieved under mild conditions, even as low as room temperature. Reactions occurred with high conversion and selectivity in many cases. Reactions can also be carried out at high temperatures in organic solvent with high selectivity using stoichiometric amounts of the alcohol.

Synthesis of Polynitrostilbenes from 2,4,6-Trinitro-M-Xylene and 2,4,6-Trinitrotoluene by a Microwave-Assisted Solvent Free Method

A microwave-assisted method for the synthesis of polynitrostilbenes involving the condensation of 2,4,6-trinitro- m-xylene and 2,4,6-trinitrotoluene with aryl aldehydes in the presence of piperidine and silica-gel is reported. Compared with conventional methods, a shorter reaction time is required and this method has a lower environmental impact. A mechanism for the reaction is also proposed and supported by UV-Vis absorption spectroscopy.

Direct α-alkylation of ketones with alcohols in water

The direct α-alkylation of ketones with alcohols has emerged as a new green protocol to construct C-C bonds with H2 O as the sole byproduct. In this work, a very simple and convenient Pd/C catalytic system for the direct α-alkylation of ketones with primary alcohols in pure water is developed. Based on this catalytic system, aqueous mixtures of dilute acetone, 1-butanol, and ethanol (mimicking ABE fermentation products) can be directly transformed into C5 -C11 or longer-chain ketones and alcohols, which are precursors to fuels.

Acid promoted cyclodehydration of amino alcohols with amide acetal

Intramolecular N-alkylation of amino alcohols using an amide acetal was developed that is widely applicable to the formation of azaheterocycles.

Sulfonated multiwalled carbon nanotubes (MWCNTs) as a new, efficient, and recyclable heterogeneous nanocatalyst for the synthesis of amines

Sulfonated multiwalled carbon nanotubes (MWCNTs) were synthesized by chemical vapor deposition (CVD) as a new and facile one-pot method using acetylene (as the CNT precursor), thiophene (as the sulfur precursor), and ferrocene (for in situ liberation of metal nanoparticles as the CNT nanocatalyst). A low catalytic amount of the resulting sulfonated MWCNTs with a turnover number (TON) up to 980 and a turnover frequency (TOF) up to 11 160 h–1 was utilized as a new and recyclable heterogeneous nanocatalyst for the efficient one-pot synthesis of various amines (secondary and tertiary) by direct reductive amination of aldehydes and ketones using NaBH4. The catalyst was easily isolated from the reaction mixture by simple filtration and reused at least five times without significant degradation in activity.