Synthesis of amino-1,4-anhydro-d-pentitols and amino-1,5-anhydro-d-hexitols with the arabino configuration from (R)-glycidol

2-Amino-1,4-anhydro-pentitol and 3-amino-1,5-anhydro-4-deoxy-hexitol with the arabino configuration were synthesised from (R)-glycidol using a metathesis reaction as the key step. The dihydrofuran or dihydropyran products obtained after the metathesis reaction were subjected to epoxidation, epoxide opening with azide anion and finally azide reduction.     

Reaction of trimethylsilyl azide with bridged bicyclic olefins

Bridged bicyclic olefins were found to undergo facile 1,3-cycloaddition reaction with trimethylsilyl azide. Norbornene produced cis,exo-1-trimethylsilyl-4,7-methano-3a,4,5,6,7,7a-hexahydrobenzotriazole, while norbornadiene formed a diadduct with cis,exo-stereochemistry, together with 2-trimethylsilyl-1,2,3-triazole produced by a retro-Diels—Alder reaction of an intermediate mono-adduct. Dicyclopentadiene reacted only at the norbornene position while α-pinene did not react with trimethylsilyl azide. In contrast to aryl- and sulfonyl-azide adducts of norbornene derivatives, which decompose upon heating the present adducts were recovered unchanged after prolonged treatment at 205°C.     

Investigation of electrochemically induced Michael addition reactions. Oxidation of some dihydroxybenzene derivatives in the presence of azide ion

In aqueous solution containing azide ion as a nucleophile, electrochemical oxidation of hydroquinone and some dihydroxybenzoic acids have been studied using cyclic voltammetry and controlled-potential coulometry. The voltammetric data show that electrochemically generated para and ortho-benzoquinones participate in Michael addition reactions with azide ions to form the corresponding diazido or diaminobenzoquinones. In this work, we have proposed various mechanisms for the electrode process and we report an efficient and one-pot method for the synthesis of 2,5-diazido-1,4-benzoquinone, 2,5-diamino-1,4-benzoquinone, 4,5-diamino-1,2-benzoquinone, and 2,3-diamino-5,6-dioxocyclohexa-1,3-dienecarboxylic acid based on the Michael reaction of electrochemically generated ortho and para-benzoquinones with azide ion in an undivided cell using an environmentally friendly reagent-less method in ambient conditions. An estimation of the observed homogeneous rate constant (k_obs) of the reaction of electrochemically generated para-benzoquinone with azide ion by the digital simulation method is also presented.     

Rapid and facile synthesis of acyl azides from acyl halides using a polymer-supported azide ion under heterogeneous conditions

In this article a rapid and facile method for synthesis of acyl azide is described. The cross-linked poly(N-methyl-4-vinylpyridinium) azide ion, [P₄-VP]N₃ is prepared and used as an efficient polymeric reagent for synthesis of acyl azides from acyl halides at room temperature under heterogeneous conditions. Various benzoyl halides, with electron-withdrawing groups as well as electron-donating groups, were transformed into the corresponding benzoyl azides in high to excellent yields in short reaction times. The acyl azide products were characterized by FT-IR, and some of them were also characterized by ¹H-and/or ¹³C-NMR spectroscopy, and physical properties were compared to literature values of known compounds. The spent polymeric reagents can be regenerated and reused for several times without losing their activity. Relative to the reported methods, the present method has the advantages of operational simplicity, mild reaction conditions, fast reaction rates, simple reaction work-up and lower hazardous and potentially explosive nature. Also the present method is the first procedure for the synthesis of acyl azides from acyl halides by using a polymer-supported azide ion under heterogeneous conditions.     

Zinc-assisted synthesis of imidazolium-tetrazolate bi-heterocyclic zwitterions with variable alkyl bridge length

Zinc halide-complexed alkyl-bridged bi-heterocycles were obtained as zwitterions from the Click reaction of a series of N-cyanoalkyl-N-alkylimidazolium halide ionic liquids with sodium azide. Reaction optimization showed fast reaction times and milder conditions compared to conventional Click syntheses from neutral nitriles.     

Decisive role of water in efficient noncatalyzed synthesis of polyfunctional 1H-1,2,3-triazoles proceeding from γ-hydroxypropynals

A highly efficient method was developed for the synthesis of new polyfunctional 1H-1,2,3-triazoles by the reaction of γ-hydroxypropynals with trimethylsilyl azide in water at room temperature without catalyst. The addition of trimethylsilyl azide to γ-hydroxypropynals occurs regioselectively: Previously unknown hydroxyalkyl-1H-1,2,3-triazolecarbaldehydes have been isolated in 69-96% yields with the prevalence of 1,5-isomers and the content of minor 1,4-isomers equal 9-21%. In the reaction of γ-hydroxypropynals with sodium azide in DMSO the formation of 4-hydroxyalkyl-1H-1,2,3-triazole-5-carbaldehydes is accompanied by the dimerization of initial aldehydes into the corresponding 1,3-dioxolanes.     

Molecular organization of reactants in the kinetics and catalysis of liquid phase reactions: XII. Mechanism of the boron trifluoride-catalyzed Curtius thermal rearrangement of benzoyl azide into phenyl isocyanate

The kinetics of the thermal decomposition and rearrangement of benzoyl azide into phenyl isocyanate was studied in n-heptane in the presence of boron trifluoride etherate as the catalyst. The apparent activation energy of the noncatalytic reaction is 28.0 kcal/mol, and that of the catalytic reaction is 11.0 kcal/mol. The electronic structure and geometry of various complexes between benzoyl azide and BF₃ were studied using the PBE/TZ2P density functional method, and fragments of the potential energy surface were calculated for the catalytic rearrangement. Comparatively stable 1: 1 and 1: 2 complexes between the syn conformer of benzoyl azide and the catalyst can form in the system by coordination to the oxygen and nitrogen atoms of the acyl azide group. The heats of formation of these complexes are between ?1.7 and ?6.4 kcal/mol. The main consequence of the formation of these complexes is that the acyl azide group comes out of the benzene ring plane and thus becomes more reactive. The effective activation energies calculated for the catalytic rearrangement involving complexes of different compositions are 12–15 kcal/mol lower the effective activation energy of the noncatalytic reaction. Information has been obtained about the structure of the transition state of the catalytic reaction, in which a nitrogen molecule is abstracted from benzoyl azide with a synchronous rearrangement of other atoms, resulting in the formation of the ultimate product.     

One-pot synthesis of 4(3H)-quinazolinones from azides, alkynes, anilines, and carbon monoxide

A one-pot synthesis of 4(3H)-quinazolinones from terminal alkynes, sulphonyl azide, o-iodoanilines, and carbon monoxide has been developed. This cascade process includes the copper-catalyzed three-component reaction of alkyne, azide and amine, the palladium-catalyzed carbonylation, and the Lewis acid catalyzed hydrolysis of sulfonamide.     

Microwave-assisted benzyne-click chemistry: preparation of 1H-benzo[d][1,2,3]triazoles

The benzotriazoles were prepared by three-component and two-component microwave-assisted [3+2] cycloadditions of various azides to benzyne, 3-methoxybenzyne, and 4,5-difluorobenzyne. In the three-component reaction, the aryne is generated, in the presence of an azide prepared in situ, by the reaction of an o-(trimethylsilylaryl) triflate with either CsF or KF/18-Crown-6. However, in the two-component reactions, a freshly prepared azide is added to the reaction vessel prior to aryne generation. Good to excellent yields of benzotriazoles were obtained in 15-20 min when the microwave-assisted reactions were carried out at 125 °C. These reaction times are significantly faster than similar reactions carried out using conventional heating.     

Reaction of N-phenyl(benzylidene,phenoxy)acetyl-1,4-benzoquinone imines with sodium azide

N-Phenyl(benzylidene, phenoxy)acetyl-1,4-benzoquinone imines reacted with sodium azide to give the corresponding 1,4-addition products, N-(4-hydroxyphenyl) carboxamides. Quantum chemical calculations showed that the initial step in the examined reaction is addition of azide ion to neutral quinone imine molecule.     

AgNO3 catalyzed synthesis of 5-substituted-1H-tetrazole via [3+2] cycloaddition of nitriles and sodium azide

An efficient one-pot, convenient catalysis for the synthesis of 5-substituted-1H-tetrazoles is reported. The [3+2] cycloaddition involves various nitriles, sodium azide in refluxing DMF and AgNO₃ as catalyst to give corresponding 5-substituted-1H-tetrazoles in good to excellent yields. It is expected that the reaction proceeds via in situ formation of a silver azide species, which participates in coordination of nitrile moiety followed by cycloaddition of azide ion to give tetrazole.     

Highly enantioselective (OC)Ru(salen)-catalyzed sulfimidation using N-alkoxycarbonyl azide as nitrene precursor

Enantioselective imidation of alkyl aryl sulfides with N-alkoxycarbonyl azide as a nitrene precursor was effected by using (OC)Ru(salen) complex 1 as catalyst. The steric and electronic nature of the N-alkoxycarbonyl group was found to strongly affect the enantioselectivity and the reaction rate, and high enantioselectivity (up to 99% ee) and good chemical yields were achieved by using 2,2,2-trichloro-1,1-dimethylethoxycarbonyl azide as the nitrene precursor at room temperature.     

Synthesis of β,β′-diamino acids from α-amino acid-derived β-lactams by ring opening with nucleophiles. Utilization in the synthesis of peptidomimetics

Ring opening of protected 3-aminoalkyl-substituted azetidin-2-ones with O-, N- or S-nucleophiles led to β,β′-diaminocarboxylic esters, amides and thioesters, respectively. The reaction outcome is improved by the addition of catalytic amounts of sodium azide. Utilization of a glycine derivative with unprotected amino function as nucleophile was possible. When bulkier amino acid esters were used, the intermediate acid azide underwent a Curtius rearrangement. The isocynates formed were trapped as the corresponding urea derivatives. Reduction of β-lactam's amide moiety led to diaminoalcohols.     

Urea mediated 5-substituted-1H-tetrazole via [3 + 2] cycloaddition of nitriles and sodium azide

A simple, new and convenient metal free procedure for the synthesis of 5-substituted 1H-tetrazoles using various nitriles and sodium azide in the presence of urea and acetic acid with good to high yields is developed. The reaction plausibly proceeds through in situ formation of urea azide active complex without toxic and/or expensive metal catalysts.     

Azidation vs [3 + 2]-cycloaddition: Chemoselective reaction of sodium azide towards o-alkynylaldehydes for the synthesis of N-heterocycles

The chemoselective synthesis of functionalized azido- and triazolo-containing nitrogen heterocycles using sodium azide and o-alkynylaldehydes has been described. The azidation reaction was preferred in acetonitrile while the [3 + 2]-cycloaddition was favored in DMSO. Furthermore, the azido-pyranoquinolines were employed for the synthesis of benzonaphthyridines via the Staudinger reaction at room temperature.     

Aqueous bile salt accelerated cascade synthesis of 1,2,3-triazoles from arylboronic acids

A facile, efficient and mild copper catalyzed strategy for cascade synthesis of various 1,4-disubstituted 1,2,3-triazoles from arylboronic acids, sodium azide and alkynes was developed by using aqueous bile salt NaDC solution as an accelerating medium. Low catalyst loading (only 1?mol% Cu source was sufficient for in situ generation of azide followed by azide–alkyne coupling), green solvent, use of bio-surfactant as additive and short reaction time make this protocol highly accessible and environment friendly.     

(-)-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.     

Catalyst-free Vicinal bromoazidation of olefins using TMSN3 and NBS

A rapid and efficient method has been developed for the synthesis of vicinal bromoazide directly from olefin using N-bromosuccinimide (NBS) and trimethylsilyl azide (TMSN₃) as the bromine and azide sources, respectively, without any catalyst in acetonitrile as solvent. The rate of reaction is remarkably fast in acetonitrile without catalyst to produce bromoazides in high yield.     

Deviations from bulk morphologies in thin films of block copolymer/additive binary blends

Deviations from bulk morphologies in thin films of binary blends of alkyne-functionalized diblock copolymer poly(ethylene oxide)-block-poly(n-butyl methacrylate-random-propargyl methacrylate) (PEO-b-P(nBMA-r-PgMA)) and Rhodamine B azide are reported, where thermal click reaction between the two components leads to microphase separated morphologies. Both in the bulk and in thin films, increasing the azide loading ratio resulted in the transition from a lamellar microdomain morphology to a hexagonally packed cylindrical mircodomain morphology. However, in thin films the lamellae-cylinder transition was observed at a different azide loading ratio, which was determined by film thickness. As a result, significant deviations from the bulk morphology were observed. These results indicate that surface interactions and confined geometry can play an important role in dictating the morphology in thin films of BCP/additive binary blends.     

Stereocontrolled synthesis of thiohydantoin spironucleosides from sugar spiroacetals

5-Epithiohydantocidin, N-alkyl and N-glycosylthiohydantoin spironucleosides are prepared from glycosylaminoesters and from furanoid and pyranoid methyl isothiocyanatoulosonates. The aminoesters and the isothiocyanates are obtained, in a stereocontrolled manner, from sugar spiroacetals through a high-yielding sequence involving ring opening with trimethyl azide, formation of an ester group, reduction of the azide, and, in the case of isothiocyanates, reaction with thiophosgene.