N-Acylbenzotriazole: convenient approach for protecting group-free monoacylation of symmetric diamines

Monatshefte für Chemie - Chemical Monthly - An efficient green route for monoacylation of aromatic diamines, namely o-phenylenediamine and p-phenylenediamine and aliphatic diamines...     

Modular approach for synthesis of vicinal diamines containing axial chiral 1,1'-binaphthyl from 1,2-diaminoethane by Pd-catalyzed N-arylation reactions

A very convenient and efficient modular approach for the synthesis of vicinal diamines containing axial chiral 1,1'-binaphthyl from 1,2-diaminoethane by Pd-catalyzed N-arylation reactions has been developed. The resulting chiral diamines could be easily converted into NHC precursors, imidazole salts, in good yields.     

Levopimaric acid derived 1,2-diamines and their application in the copper-catalyzed asymmetric Henry reaction

Levopimaric acid, a readily available starting material, was used in efficient syntheses of new enantiopure diamines and Schiff bases with good yields. The synthetic procedure is based on the fumaropimaric acid monomethyl ester conversion into the optically pure trans-1,2-diamine via a Curtius rearrangement. New diamines were studied as ligands in the copper-catalyzed asymmetric Henry reaction.     

Effective ring-opening reaction of aziridines with trimethylsilyl compounds: A facile access to beta-amino acids and 1,2-diamine derivatives

Ring-opening reactions of aziridines with trimethylsilyl compounds triggered by tetrabutylammonium fluoride give the corresponding products regioselectively in excellent yield. It provides a facile and efficient procedure for the ring-opening reactions of aziridines and affords a practical access to the synthesis of cyano-, azido-, or chloroamines because of its efficiency and simplicity. The products are easily transformed to vicinal diamines or beta-amino acids.     

Photoinduced Olefin Diamination with Alkylamines

Vicinal diamines are ubiquitous materials in organic and medicinal chemistry. The direct coupling of olefins and amines would be an ideal approach to construct these motifs. However, alkene diamination remains a long‐standing challenge in organic synthesis, especially when using two different amine components. We report a general strategy for the direct and selective assembly of vicinal 1,2‐diamines using readily available olefin and amine building blocks. This mild and straightforward approach involves in situ formation and photoinduced activation of N‐chloroamines to give aminium radicals that enable efficient alkene aminochlorination. Owing to the ambiphilic nature of the β‐chloroamines produced, conversion into tetra‐alkyl aziridinium ions was possible, thus enabling diamination by regioselective ring‐opening with primary or secondary amines. This strategy streamlines the preparation of vicinal diamines from multistep sequences to a single chemical transformation.     

Enantioselective construction of quaternary carbon centre catalysed by bifunctional organocatalyst

The bifunctional thiourea-tertiary amine derivatives of simple chiral diamines serve as highly enantioselective catalysts for the Michael addition of alpha-substituted cyanoacetates to vinyl sulfones, giving an efficient protocol for the construction of an all-carbon substituted quaternary stereocentre.     

Preparation of Polyimides Via the Palladium-Catalyzed Carbonylation and Condensation of Tetraiodoaromatics and Diamines

Several polyimides were prepared by the palladium-catalyzed carbonylation and condensation of tetraiodoaromatic compounds and diamines. This new reaction for preparing polyimides was verified in model compound work to be an efficient, high yield route to cyclic imides. Since fully imidized groups are formed during the polymerization, it was necessary to limit the diamines to those that would impart solubility to the polymer. In contrast to the model compound work, the polymerization reaction yielded an appreciable concentration of amide functional groups due to incomplete cyclization and/or branching reactions. Thermal characterization of the polyimides formed by this process is reported.     

An investigation into the role of polarity of diamines in controlling the electron migration mechanism of photoluminescent poly(amide–imide)s

Several diamines with remarkable different polarities were used to produce photoactive poly(amide–imide)s (PAI)s in a quantitative yield. The absorption, fluorescence and photophysical properties of series of poly(amide–imide)s containing fused aromatic systems as energy donor and energy acceptor with different diamines cores are described. Poly(amide–imide)s exhibit broad fluorescent characteristic, and its fluorescent intensity is related to the intermolecular chain–chain or chain–solvent interaction. The fluorescence spectra confirmed an efficient singlet–singlet energy transfer between fused aromatic systems. The self-quenching mechanism was studied according to the specific behavior of these polymers in different solvents. The self-quenching rate constant for the association reaction in the excited state (Kq) could be measured from the Stern–Volmer equation. The kind of fused system and diamines show different electron migration mechanisms and photoluminescent properties in the singlet-excited states. By using the exothermic energy transfer as a function of diamine polarity, the electron transfer mechanism was evaluated for aromatic poly(amide–imide)s. In principle, the fluorescence energy is absorbed by different (PAI)s and raises the molecules to one of its excited states. Afterwards this excitation energy transfers through the different relaxation channels, i.e. columbic or exchange energy transfer.     

Samarium diiodide-induced asymmetric synthesis of optically pure unsymmetrical vicinal diamines by reductive cross-coupling of nitrones with N-tert-butanesulfinyl imines

[reaction: see text] An efficient method for the preparation of optically pure unsymmetrical vicinal diamines by the SmI(2)-induced reductive cross-coupling of nitrones with chiral N-tert-butanesulfinyl imines was developed. This is the first successful example of the highly diastereoselective and enantioselective cross-coupling between two different imine species. It provides a straightforward access to enantiopure unsymmetrical vicinal diamines that are widely applicable in asymmetric synthesis.     

Synthesis of azabicyclo[n.1.0]alkane-derived bifunctional building blocks via the Corey–Chaykovsky cyclopropanation

An efficient approach towards the synthesis of monoprotected azabicyclo[5.1.0]octane-derived conformationally restricted γ-amino acids and diamines is reported. Optimization of the conditions for the key Corey–Chaykovsky reaction allowed the construction of two isomeric methanoazepane frameworks on a multigram scale in 55–65% yield. Additionally, the developed approach was used in the three-step synthesis of 3,4-methano-β-proline and its diamine derivatives.     

Divergent 2-Chloroquinazolin-4(3H)-one Rearrangement: Twisted-Cyclic Guanidine Formation or Ring-Fused N-Acylguanidines via a Domino Process

A highly efficient 2-chloroquinazolin-4(3H)-one rearrangement was developed that predictably generates either twisted-cyclic or ring-fused guanidines in a single operation, depending on the presence of a primary versus secondary amine in the accompanying diamine reagent. Exclusive formation of twisted-cyclic guanidines results from pairing 2-chloroquinazolinones with secondary diamines. Use of primary amine-containing diamines permits a domino quinazolinone rearrangement/intramolecular cyclization, gated through (E)-twisted-cyclic guanidines, to afford ring-fused N-acylguanidines. This scalable, structurally tolerant transformation generated 55 guanidines and delivered twisted-cyclic guanidines with robust plasma stability and an abbreviated total synthesis of an antitumor ring-fused guanidine (4 steps, 55 % yield).     

A facile,one-pot procedure for the formation of benzimidazoles from esters using DABAL-Me3, an air stable source of AlMe3

A convenient, single-step, efficient synthesis of benzimidazoles from esters and diamines is reported. The methodology uses an air stable form of trimethylaluminum referred to as DABAL-Me₃ and is compatible with a wide range of functional groups, including acid-sensitive protecting groups.     

Tandem aza-Michael additions under high pressure: a shortcut to the azanorbornyl skeleton

The hyperbaric aza-Michael addition of mono- and diamines on α,β-unsaturated β,β-disubstituted mono- and diesters has been studied. While in the case of monoester, this reaction provides a β-aminoester presenting a quaternary center, a direct and efficient access to diester or lactams featuring an azanorbornyl skeleton was obtained when starting from a diester, following an unprecedented double aza-Michael addition.     

Synthesis of benzimidazole and quinoxaline derivatives using reusable sulfonated rice husk ash (RHA-SO3H) as a green and efficient solid acid catalyst

Research on Chemical Intermediates - In this work, a simple, rapid and efficient method for the preparation of benzimidazoles and quinoxalines from the condensation of o-phenylene diamines with...     

An Efficient Synthesis of Spiroquinoxalinones via Tandem Reactions

A mild and efficient synthesis of spiroquinoxalinones via tandem condensation of chlorooxoindoline 1 with benzene‐1,2‐diamines 2 is described. And a plausible mechanism for the reaction is proposed.     

Microwave-assisted one step high-throughput synthesis of benzimidazoles

One-pot synthesis of benzimidazoles from diamines and carboxylic acids was developed under microwave irradiation condition, which provided a practical and efficient method for high-throughput synthesis of this important class of heterocyclic compounds.     

Effect of tertiary diamines on anionic polymerization of polar vinyl monomers

Tertiary diamines that exhibit chelating capability to lithium are shown to decrease the reactivity of growing species when used in classical anionic polymerization of methacrylic monomers. Out of the different diamines investigated, sparteine turns out to be the most efficient chelating agent. The beneficial effect of the latter additives on the overall reactivity of methacrylic anions was exploited to prepare poly(MMA) samples of controlled size at room temperature. The decrease in reactivity was also demonstrated from a kinetic point of view, upon measuring the actual rate constant of propagation using vinyl pyridine as model monomer.     

An Efficient and Convenient Synthesis of Imidazolines and Benzimidazoles via Oxidation of Carbon‐Nitrogen Bond in Water Media

The metal coordination complex K₄[Fe(CN)₆] is an efficient and environmentally benign catalyst for the synthesis of imidazolines and benzimidazoles from various aldehydes and 1,2‐diamines in aqueous medium at room temperature. This protocol gives excellent yield of product with desired purity.     

New C2-symmetrical ferrocenyl diamines as ligands for ruthenium catalyzed transfer hydrogenation

The new C₂-symmetrical ferrocenyl diamines 5–7 and 13 proved to be good ligands for the ruthenium catalyzed enantioselective transfer hydrogenation of unsymmetrical ketones. The stereocontrolled and highly flexible synthetic route to the new diamines made it possible to vary the ligand structure in an efficient manner. A short trial and error process led to a very active catalytic system with diamine 6a as the ligand, which is capable of reducing ketones even at −30°C using 2-propanol as a hydrogen source. Enantioselectivities up to 90% were reached in the reduction of 1′-acetonaphthone.     

Secondary-secondary diamine catalysts for the enantioselective Michael addition of cyclic ketones to nitroalkenes

Secondary-secondary diamines derived from S-proline are efficient catalysts for the ketone-nitroalkene Michael addition reaction. The stereoselectivity of the Michael addition is dependant on the pK_a of the N-substituted aminomethyl pendant in these diamines. N′-Aryl aminomethyl pyrrolidines provide γ-nitroketones with moderate to good enantiomeric excess (65-92%). Removal of the hydrogen-bond donor group by N-methylation results in a dramatic reduction of enantioselectivity (average ee 6%).