Azide Source Research Articles

SNAr azidation of phenolic functions utilizing diphenyl phosphorazidate

A useful method for the synthesis of aryl azides via SNAr reaction of phenol derivatives using diphenyl phosphorazidate (DPPA) as an azidation reagent was developed. Various phenol derivatives bearing electron-withdrawing groups were converted into the corresponding aryl azides in a single step. This method is easy to perform and enables the preparation of aryl azides without the use of explosive azide sources.

Synthesis of hydroxyethyl methyl morpholinium azide (HEM Morph)N3: A highly efficient new task specific azide-based ionic liquid and its dual application as an azide source and media for synthesis of some novel aromatic O-oxime ethers-1,2,3-triazole conjugates as a potential antihistaminic agents

The synthesis, characterization and application of hydroxyethyl methyl morpholinium azide (HEM Morph)N3 as a new azide-based ionic liquid (ABIL) has been described. (HEM Morph)N3 is used as a source of azide and reaction media for three components ‘Click’ Huisgen cycloaddition reaction between O-propargyl oxime ether and alkyl bromide to acquire novel aromatic O-oxime ethers-1,2,3-triazole conjugates as potential antihistaminic agents in good yields. The influence of parameters like temperature, amount of IL, type of azide-based ionic liquids and its reusability is investigated. The (HEM Morph)N3 is proved to be an efficient, thermally stable, inexpensive and recyclable azide-based ionic liquid which can be easily synthesized and used as both azide's source and reaction media for ‘Click’ Huisgen cycloaddition reaction.

Synthesis of N-heterocycles containing 1,5-disubstituted-1H-tetrazole via post-Ugi-azide reaction.

Ugi-azide four-component reaction (UA-4CR) as development on Ugi four-component reaction (U-4CR) is the condensation reaction involving an aldehyde, an amine, an isocyanide, and an azide source. Nowadays, UA-4CR has been employed for the efficient and facile production of 1,5-disubstituted-1H-tetrazoles (1,5-DS-1H-Ts). Interestingly, the combination of 1,5-DS-1H-Ts with suitable post-transformations in a tandem manner results in the construction of various classes of heterocyclic compounds bearing 1,5-DS-1H-T moiety. This review aims to provide the application of diverse post-Ugi-azide reaction in the preparation of different N-heterocyclic compounds bearing 1,5-DS-1H-T such as substituted and fused 1,5-DS-1H-Ts.

Stereospecific synthesis of 1,5-disubstituted tetrazoles from ketoximes via a Beckmann rearrangement facilitated by diphenyl phosphorazidate

A novel method for the stereospecific synthesis of 1,5-disubstituted tetrazoles from ketoximes via the Beckmann rearrangement was developed using diphenyl phosphorazidate (DPPA) as both the oxime activator and azide source. Various ketoximes were transformed into the corresponding 1,5-disubstituted tetrazoles with exclusive trans-group migration and no E-Z isomerization of the ketoxime. This method enables the preparation of 1,5-disubstituted tetrazoles without using toxic or explosive azidation reagents.

Radical ring opening reaction of pyridine fused heterocycles with IBA-N3 catalyzed by tetra-n-butylammonium iodide

A mild, metal-free and efficient synthesis of 2,3-disubstituted acrylonitriles and α-iminonitriles through radical ring opening reaction of pyridine fused heterocycles has been developed. The tetra-n-butylammonium iodide catalyst acts as a formal one-electron donor. Compared to the previous methods, which require excessive amounts of highly explosive azide sources and the addition of oxidants, this is a safe and convenient transformation.

Double Cu-Catalyzed Direct Csp3 -H Azidation/CuAAC Reaction: A Direct Approach towards Demanding Triazole Conjugates.

The first one-pot procedure for the double copper(I)-catalyzed oxidative Csp3 -H azidation-CuAAC process, implying unstable azide intermediates and easy-to-remove reagents under water-tolerant conditions, is presented. The combination of tert-butyl hydroperoxide as oxidant and TMSN3 as azide source for the C-H bond azidation, which produces harmless side-products such as tBuOH and H2 O, probed to be perfectly compatible with the following cycloaddition step. Highly demanding 1,2,3-triazoles could be then directly obtained in good overall yields by extraction or simple crystallization, thus avoiding chromatography purifications. The potential of this methodology, has also being highlighted by the successful reaction of alkynes presenting interesting complex biological moieties based for example on biotin, DNA base or cinchona alkaloid units.

Cyclic Hypervalent Iodine Reagents for Azidation: Safer Reagents and Photoredox-Catalyzed Ring Expansion.

Azides are building blocks of increasing importance in synthetic chemistry, chemical biology, and materials science. Azidobenziodoxolone (ABX, Zhdankin reagent) is a valuable azide source, but its safety profile has not been thoroughly established. Herein, we report a safety study of ABX, which shows its hazardous nature. We introduce two derivatives, tBu-ABX and ABZ (azidobenziodazolone), with a better safety profile, and use them in established photoredox- and metal-mediated azidations, and in a new ring-expansion of silylated cyclobutanols to give azidated cyclopentanones.

Mild Dirhodium(II)-Catalyzed Chemo- and Regioselective Azidation of Arenes.

A mild chemo- and regioselective aromatic azidation reaction catalyzed by a dirhodium(II) catalyst with Zhdankin's reagent as the azide source is described. A variety of functional groups were well tolerated under the reaction conditions. Mechanistic studies suggested that the Rh2(II,II)-bound azide intermediate, rather than the free azide radical, is the key active species in the reaction.

Copper(II)-Catalyzed Reactions of α-Keto Thioesters with Azides via C-C and C-S Bond Cleavages: Synthesis of N-Acylureas and Amides.

Cu(II)-catalyzed reaction of α-keto thioesters with trimethylsilyl azide (TMSN3) proceeds with the transformation of the thioester group into urea through C-C and C-S bond cleavages, constituting a practical and straightforward synthesis of N-acylureas. When diphenyl phosphoryl azide (DPPA) is used instead as the azide source in an aqueous environment, primary amides are formed via substitution of the thioester group. The reactions are proposed to proceed through Curtius rearrangement of the initially formed α-keto acyl azide to generate an acyl isocyanate intermediate, which reacts further with an additional amount of azide or water and rearranges to afford the corresponding products. To demonstrate the potentiality of the method, one-step syntheses of pivaloylurea and isovaleroylurea, displaying anticonvulsant activities, have been carried out.

Pummerer rearrangement using bis(p-nitrophenyl) phosphorazidate as an azidation reagent: A novel synthesis of azidomethyl sulfides

A novel method for the synthesis of azidomethyl sulfides by Pummerer rearrangement using bis(p-nitrophenyl) phosphorazidate (p-NO2DPPA) as an azidation reagent was developed. Various methyl sulfoxides were converted into the corresponding azidomethyl sulfides. Importantly, this reaction enables the preparation of azidomethyl sulfides without the use of toxic or explosive azide sources.

Divergent Access to (1,1) and (1,2)-Azidolactones from Alkenes using Hypervalent Iodine Reagents.

A versatile synthesis of azidolactones through azidation and cyclization of carboxylic acids onto alkenes has been developed. Based on either photoredox or palladium catalysis, (1,1) and (1,2) azido lactones can be selectively synthesized. The choice of catalyst and benziodoxol(on)e reagent serving as azide source was essential to initiate either a radical or Lewis acid mediated process with divergent outcome. These transformations were carried out under mild conditions using a low catalyst loading and gave access to a large scope of azido lactones.

Palladium‐Catalyzed Intermolecular Oxidative Diazidation of Alkenes

AbstractA palladium‐catalyzed oxidative vicinal diazidation of alkenes has been developed, in which TMSN3 was used as azide source. Both styrenes and unactivated alkenes are suitable for this reaction. And trans‐alkyldiazides were obtained as major products from cyclic alkenes with moderate to good diastereoselectivities. This reaction afforded an efficient way for the synthesis of useful 1,2‐diamines after hydrogenation.

A reliable one-pot synthesis of aryl azides from aryl amines using organotin azides as effective and recoverable reagents

A mild and mass-efficient procedure based on the one-pot diazotization-azidodediazoniation of aromatic amines is described. A wide range of aryl azides are obtained in moderate to high yields by using tributyltin azide as an effective and reusable azide source in the presence of p-toluenesulfonic acid at room temperature. The method was also successfully applied employing an insoluble polymer-supported organotin azide.

ChemInform Abstract: Copper‐Catalyzed Intermolecular Chloroazidation of α,β‐Unsaturated Amides.

A highly practical copper-catalyzed intermolecular chloroazidation of α,β-unsaturated amides has been described, giving a series of azidochlorides in good-to-excellent yields. The stable azidoiodine(iii) reagent and SOCl2 were used as azide and chlorine sources, respectively. The synthetic applications of this protocol were also explored by a variety of synthetically useful transformations.

Highly efficient three-component synthesis of 5-substituted-1H-tetrazoles from aldehydes, hydroxylamine, and tetrabutylammonium azide using doped nano-sized copper(I) oxide (Cu2O) on melamine–formaldehyde resin

A simple and facile one-pot three-component synthesis of 5-substituted 1H-tetrazole derivatives from aldehydes catalyzed by doped nano-sized Cu2O on melamine–formaldehyde resin (nano-Cu2O–MFR) is described. In this protocol, treatment of structurally diverse aldehydes, hydroxylamine hydrochloride and tetrabutylammonium azide (TBAA) as an azide source in the presence of nano-Cu2O–MFR as an efficient heterogeneous nano-catalyst affords the corresponding 5-substituted 1H-tetrazoles in good to excellent yields. The influence of different parameters on the progress of reaction was studied. The nano-Cu2O–MFR is a cheap and stable nano-catalyst that could be easily prepared, recycled and reused for many consecutive reaction runs without significant decrease in its activity.

Ultrasound promoted mild and facile one-pot, three component synthesis of 2H-indazoles by consecutive condensation, C[sbnd]N and N[sbnd]N bond formations catalysed by copper-doped silica cuprous sulphate (CDSCS) as an efficient heterogeneous nano-catalyst

An ultrasonic promoted facile and convenient one-pot three-component procedure for the synthesis of 2H-indazole derivatives using copper-doped silica cuprous sulphate (CDSCS) as a heterogeneous nano-catalyst has been described. In this approach, ultrasonic mediated reaction of different substituted 2-bromobenzaldehydes, structurally diverse primary amines, and tetrabutylammonium azide (TBAA) as an azide source in the presence of CDSCS in DMSO at room temperature furnishes 2H-indazoles in good to excellent yields. Utilizing ultrasonic irradiation techniques provided the dramatic improvements in terms of higher yields and shorter reaction times compared with conventional heating method.

Convergent Three‐Component Tetrazole Synthesis

AbstractA microwave‐accelerated, simple, and efficient method for the construction of the 1,5‐tetrazole scaffold was developed. It comprises a multicomponent reaction of an amine, a carboxylic acid derivative, and an azide source. On the basis of the availability of the archetypical starting materials, this method provided very versatile synthetic access to 1,5‐disubstituted tetrazoles. The usefulness of this method was demonstrated in the synthesis of biologically important fused tetrazole scaffolds and the marketed drug cilostazol.

ChemInform Abstract: Copper‐Catalyzed Vicinal Oxyazidation and Diazidation of Styrenes under Mild Conditions: Access to Alkyl Azides.

AbstractA novel vicinal oxyazidation and diazidation of styrenes (I) using the stable azidoiodine reagent (II) as an azide source is described.

Copper-catalyzed intermolecular chloroazidation of α,β-unsaturated amides.

A highly practical copper-catalyzed intermolecular chloroazidation of α,β-unsaturated amides has been described, giving a series of azidochlorides in good-to-excellent yields. The stable azidoiodine(iii) reagent and SOCl2 were used as azide and chlorine sources, respectively. The synthetic applications of this protocol were also explored by a variety of synthetically useful transformations.

Transition-Metal-Free Oxidative Aliphatic C-H Azidation.

The first example of a practical and selective azidation of unactivated aliphatic C-H bonds with easily handled sulfonyl azides as azide source without the use of transition metals has been explored. This method is operationally simple, scalable, and applicable to late-stage azidation of natural products and derivatives, which make it a valuable method for the synthesis of organic azides.