Condensation of <Emphasis Type="Italic">N</Emphasis>-(2-vinyloxyethyl)ethane-1,2-diamine with carbonyl compounds

Condensation of N-(2-vinyloxyethyl)ethane-1,2-diamine with aromatic aldehydes gave mixtures of 2-aryl-1-(2-vinyloxyethyl)imidazolidines and N-arylmethylidene-N′-(2-vinyloxyethyl)ethane-1,2-diamines in an overall yield of 79–84%, while analogous condensation with cyclic and acyclic ketones resulted in the formation of only the corresponding Schiff bases (yield 53–83%).     

Chemosensors based on N-(9-anthrylmethyl)-benzene-1,2-diamine

A number of N-(9-antrylmethyl)-N′-arylmethylidenebenzene-1,2-diamines and 1-(9-anthrylmethyl)-2-aryl-1H-benzimidazoles were synthesized by condensation of N-(9-anthrylmethyl)benzene-1,2-diamine with aromatic and heterocyclic aldehydes. Study on their luminescent properties and complexing ability showed that 2-{[2-(9-anthrylmethylamino)phenylimino]methyl}-5-methylphenol, 2-{[2-(9-anthrylmethylamino)phenylimino] methyl}-4-methoxyphenol, and 2-{[2-(9-anthrylmethylamino)phenylimino]methyl}-6-methoxy-4-nitrophenol are effective and highly selective chemosensors for H⁺ and Hg²⁺ ions.     

Solvent-dependent enantioswitching in the Michael addition of α,α-disubstituted aldehydes to maleimides organocatalyzed by mono-N-Boc-protected cyclohexa-1,2-diamines

Enantiomerically pure mono-N-Boc-protected trans-cyclohexa-1,2-diamines are used as organocatalysts for the enantioselective conjugate addition of α,α-disubstituted aldehydes to maleimides. Using a single enantiomer of the organocatalyst, both enantiomeric forms of the resulting Michael adducts bearing a new quaternary stereocenter are obtained in high yields, by only changing the reaction solvent from chloroform (up to 86% ee) to aqueous DMF (up to 84% ee).     

NHC-initiated cascade,metal-free synthesis of quinoxaline derivatives under solvent-free conditions

2,3-Diaryl quinoxaline derivatives have been efficiently synthesized by cascade, metal-free, and solvent-free reaction of aryl aldehydes with aryl 1,2-diamines initiated by N-heterocyclic carbene. Compared with reported methods, this procedure has the advantages of easy work-up, reduced energy consumption, and elimination of solvent waste, hazards, and toxicity. A group of potentially bioactive compounds has been prepared for biomedical screening.     

Synthesis and derivatisation of N,N′-trisubstituted 1,2-diamines derived from (1R,2R)-1,2-diaminocyclohexane

The synthesis of N,N′-trisubstituted 1,2-diamines can be achieved by simple reduction of an aminal derived from (1R,2R)-diaminocyclohexane. We comment on the scope and limitation of this reduction and discuss its application towards the synthesis of unsymmetrical N,N′-tetrasubstituted 1,2-diamines.     

N-Cyanomethyl-β-chloroamines: a convenient source of aziridinium ions

N-Cyanomethyl-β-chloroamines smoothly react with a range of alcohols or amines to give regio- and stereoselectively 1,2-aminoethers or 1,2-diamines. The reaction proceeds through the formation of an intermediate aziridinium ion. The N-cyanomethyl group can then be cleaved easily.     

Synthesis of N,N′-disubstituted cyclic 1,2-diamines derived from (1R,2R)-1,2-diaminocyclohexane

The synthesis of N,N′-unsymmetrically tetrasubstituted cyclic 1,2-diamines derived from (1R,2R)-diaminocyclohexane is reported. We comment on the structural nature of these cyclic 1,2-diamines and discuss their characteristic features.     

Synthesis of new chiral cyclic 1,2-diamines and their evaluation as catalysts for enantioselective Diels-Alder reactions

The synthesis of new, enantiomerically pure cyclic 1,2-diamine structures was realized through a zinc promoted coupling of chiral bis-imines easily prepared starting from a chiral biphenyl dicarboxylic acid. The catalytic properties of such novel compounds were preliminarily studied; the trifluoroacetate salts of these chiral 1,2-diamines were shown to be able to catalyze the Diels-Alder reaction between cyclopentadiene and α,β-unsaturated aldehydes with good exo stereoselectivity and enantioselectivities up to 71%.     

McMurry coupling of aryl aldehydes and imino pinacol coupling mediated by Ti(O-i-Pr)4/Me3SiCl/Mg reagent

Ti(O-i-Pr)₄/Me₃SiCl/Mg reagent mediated McMurry coupling of aryl aldehydes to biaryl olefins at near room temperature. This low valent titanium (LVT) reagent also mediated the coupling of aldimines to 1,2-diamines (imino pinacol coupling).     

New N,N-diamine ligands derived from (−)-menthol and their application in the asymmetric transfer hydrogenation

Natural (?)-menthol was applied to construction of mono-N-tosylated-1,2-diamine derivatives. The O-tosylation and elimination of the tosylate of the menthol intermediate led to trans-p-menth-2-ene. The unsaturated menth-2-ene was next transformed into a mixture of N-tosylaziridines, which upon reaction with sodium azide gave four isomeric azides. The reduction of the formed tosylazides on Pd/C gave new chiral mono-N-tosylated-1,2-diamines, which were used as ligands in the asymmetric transfer hydrogenation protocol on aromatic ketones and endocyclic imine.     

Enantioselective Michael addition of aldehydes to maleimides organocatalysed by chiral 1,2-diamines: an experimental and theoretical study

Simple and commercially available chiral 1,2-diamines were used as organocatalysts for the enantioselective conjugate addition of aldehydes, including α,α-disubstituted, to maleimides. The reaction was carried out in the presence of hexanedioic acid as an additive in aqueous solvents at room temperature. By employing (1S,2S)- and (1R,2R)-cyclohexane-1,2-diamine as organocatalysts, the corresponding Michael adducts bearing new stereocenters were obtained in high or quantitative yields with enantioselectivities of up to 92%, whereas the use of (1S,2S)-1,2-diphenylethane-1,2-diamine gave a much lower ee. Theoretical calculations were used to justify the observed sense of the stereoinduction.     

A facile one-pot synthesis of 2-fluoroalkyl 1,3-imidazolines and 1,3-oxazolines through imidoyl halide intermediates

A facile one-pot procedure has been developed for the synthesis of 1,3-imidazolines and 1,3-oxazolines bearing fluorinated alkyl groups at the 2-position. The reaction involves the condensation of N-monosubstituted ethane-1,2-diamines or 2-aminoethanols with a fluorinated carboxylic acid in the presence of PPh₃/CX₄. The proposed mechanism is that the amide intermediates were initially formed, and then converted to the imidoyl halide intermediates in the presence of PPh₃/CX₄, followed by rapid intramolecular cyclization to 1,3-diazoline products. This protocol allows for the synthesis of 2-bromodifluoromethyl-1,3-imidazoline, a useful CF₂Br-heterocyclic building block, which can be used for the synthesis of gem-difluoromethylene linked compounds.     

Synthesis of new mono-N-tosylated diamine ligands based on (R)-(+)-limonene and their application in asymmetric transfer hydrogenation of ketones and imines

A synthetic procedure leading to the preparation of a new family of enantiopure mono-N-tosylated-1,2-diamines derived from (R)-(+)-limonene is described. (+)-Limonene was transformed into the appropriate N-tosyl derivative using N-tosylaziridination based on chloramine-T trihydrate. Subsequent ring opening by sodium azide afforded the corresponding isomeric azides. Finally, reduction of the azide function gave enantiomerically pure mono-N-tosylated-1,2-diamines. The ligands obtained proved to be effective in the asymmetric transfer hydrogenation protocol on aromatic ketones and imines.     

An efficient synthetic route to substituted tetrahydropyrimidines by Cu(OTf)2-mediated nucleophilic ring-opening followed by the [4+2] cycloaddition of N-tosylazetidines with nitriles

A highly efficient strategy for Cu(OTf)₂-mediated S_N2 type nucleophilic ring-opening followed by the [4+2] cycloaddition reactions of a number of 2-aryl-N-tosylazetidines with nitriles to afford a variety of substituted tetrahydropyrimidines in excellent yields is reported. The resulting tetrahydropyrimidines could easily be transformed into synthetically important 1,3-diamines by acid-catalyzed hydrolysis. The strategy has been extended to the synthesis of enantiomerically pure tetrahydropyrimidines from enantiopure disubstituted azetidines. The reaction proceeds through an S_N2 type mechanism as proposed by us earlier.     

Synthesis of enamino ketones from <Emphasis Type="Italic">N</Emphasis>-(2-vinyloxyalkyl)-ethane-1,2-diamines

Condensation of N-(2-vinyloxyethyl)ethane-1,2-diamine with aromatic aldehydes gave mixtures of 2-aryl-1-(2-vinyloxyethyl)imidazolidines and N-arylmethylidene-N′-(2-vinyloxyethyl)ethane-1,2-diamines in an overall yield of 79–84%, while analogous condensation with cyclic and acyclic ketones resulted in the formation of only the corresponding Schiff bases (yield 53–83%).     

A one-pot four-component synthesis of N-arylidene-2-aryl-imidazo[1,2-a]azin-3-amines

N-Arylidene-2-aryl-imidazo[1,2-a]azin-3-amines were synthesized via a one-pot, four-component condensation reaction using a 2-aminoazine, toluene-4-sulfonylmethyl isocyanide (TsCH₂NC), and two equivalents of readily available aromatic aldehydes. The reaction was performed in diethyl ether as the solvent, with p-toluenesulfonic acid (p-TSA) as the catalyst at reflux temperature.     

An efficient chemoenzymatic method to prepare optically active primary-tertiary trans-cycloalkane-1,2-diamines

Optically active trans-N-Boc-cyclopentane- and cyclohexane-1,2-diamines (7) were prepared by a chemoenzymatic method from the corresponding (±)-trans-N,N-diallylcycloalkane-1,2-diamine. These mono-carbamates 7 (ee=99%) were used as the starting materials in the syntheses of different vicinal primary-tertiary diamines. Thus, by means of a simple three-step sequence involving a reductive-amination of an aromatic aldehyde with 7, N-methylation and finally, cleavage of the Boc group, several trans-N-(arylmethyl)-N-methylcyclopentane- and cyclohexane-1,2-diamines were obtained in high yields.     

Addition of allyltrichlorostannanes to aldehydes: application in the synthesis of 4-N-Boc-amino-3-hydroxy ketones

We wish to describe here the diastereoselective reaction between chiral N-Boc-α-amino aldehydes and achiral allyltrichlorostannanes leading to 1,2-syn-N-Boc-α-amino alcohols, which are treated with catalytic amounts of OsO₄ in the presence of NaIO₄ to provide the corresponding 4-N-Boc-amino-3-hydroxy ketones.     

A Keggin heteropoly acid as an efficient catalyst for an expeditious, one-pot synthesis of 1-methyl-2-(hetero)arylbenzimidazoles

The Keggin heteropoly acid, silicotungstic acid, H₄SiW₁₂O₄₀, has been demonstrated to be highly efficient for an expeditious, one-pot synthesis of 1-methyl-2-(hetero)arylbenzimidazoles from N-methyl-1,2-phenylenediamine and (hetero)aryl aldehydes in ethyl acetate at room temperature. The catalyst works equally well for N-phenyl-1,2-phenylenediamine.     

(-)-Menthol as a source of new N,N-diamine ligands for asymmetric transfer hydrogenation

The synthesis of new chiral N-monotosylated-1,2-diamines based on the (-)-menthol skeleton is presented. The elimination of HCl from neomenthyl chloride obtained from an Appel reaction led to p-menth-3-ene in excellent yield. Further functionalization of the double bond in p-menth-3-ene with chloramine-T gave the corresponding N-tosylaziridines, which upon reaction with sodium azide and subsequent reduction of the azide functional group, formed the 1,2-diamine system. The synthesized chiral ligands proved effective in the asymmetric transfer hydrogenation of aromatic ketones and an endocyclic imine.