Developments on the Chemistry of Tellurium and Selenium Azides

Abstract

We have been carrying out systematic studies on the preparation and properties of tellurium halide and pseudohalide compounds with a focus on tellurium azides. We were successful in the synthesis of various tellurium azides of both covalent and ionic nature. Several tellurium(IV) azides, tellurium(II) azides, and the first tellurium(VI) azides can be prepared in reasonable amounts. The first structural information of selenium azides is obtained for covalent and ionic derivatives, and spectroscopic data for the existence of selenium(iv) polyazides.     

Glycosylthiomethyl chloride: a new species for S-neoglycoconjugate synthesis. Synthesis of 1-N-glycosylthiomethyl-1,2,3-triazoles

Reaction of O-acyl-protected glycosylthiols with dichloromethane afforded readily glycosylthiomethyl chlorides, which gave with sodium azide the corresponding glycosylthiomethyl azides 17-22. Reaction of these azides with dicyclopentadiene as dipolarophile led to tandem 1,3-dipolar cycloaddition/retro-Diels-Alder reaction furnishing the parent 1-glycosylthiomethyl-1,2,3-triazoles 23-25. Reaction of azides with acetylene derivatives gave directly 1-glycosylthiomethyl-1,2,3-triazoles which are ring-substituted.     

Chemoselectivity of Tertiary Azides in Strain-Promoted Alkyne-Azide Cycloadditions

The strain-promoted alkyne-azide cycloaddition (SPAAC) is the most commonly employed bioorthogonal reaction with applications in a broad range of fields. Over the years, several different cyclooctyne derivatives have been developed and investigated in regard to their reactivity in SPAAC reactions with azides. However, only a few studies examined the influence of structurally diverse azides on reaction kinetics. Herein, we report our investigations of the reactivity of primary, secondary, and tertiary azides with the cyclooctynes BCN and ADIBO applying experimental and computational methods. All azides show similar reaction rates with the sterically non-demanding cyclooctyne BCN. However, due to the increased steric demand of the dibenzocyclooctyne ADIBO, the reactivity of tertiary azides drops by several orders of magnitude in comparison to primary and secondary azides. We show that this chemoselective behavior of tertiary azides can be exploited to achieve semiorthogonal dual-labeling without the need for any catalyst using SPAAC exclusively.     

The electronic absorption spectra of some acyl azides molecular orbital treatment

The electronic absorption spectra of benzoyl azide and its derivatives: p-methyl, p-methoxy, p-chloro and p-nitrobenzoyl azide were investigated in different solvents. The observed spectra differ basically from the electronic spectra of aryl azides or alkyl azides. Four intense pi-pi* transitions were observed in the accessible UV region of the spectrum of each of the studied compounds. The contribution of charge transfer configurations to the observed transitions is rather weak. Shift of band maximum with solvent polarity is minute. On the other hand, band intensity is highly dependent on the solvent used. The observed transitions are delocalized rather than localized ones as in the case with aryl and alkyl azides. The attachment of the CO group to the azide group in acyl azides has a significant effect on the electronic structure of the molecule. The arrangements as well as energies of the molecular orbitals are different in acyl azides from those in aryl azides. The first electronic transition in phenyl azide is at 276 nm, whereas that of bezoyle azide is at 251 nm. Ab initio molecular orbital calculations using both RHF/6-311G* and B3LYP/6-31+G* levels were carried out on the ground states of the studied compounds. The wave functions of the excited states were calculated using the CIS and the AM1-CI procedures.     

THE PHOTOCHEMISTRY OF ACETYL-SUBSTITUTED AROYL AZIDES: THE DESIGN OF PHOTOLABELING AGENTS FOR INERT SITES IN HYDROPHOBIC REGIONS

The photochemistry, photophysics and hydrolytic stability of three substituted aroyl azides were investigated. The azides were selected as model compounds for potential photolabeling agents based on the extreme electrophilic reactivity of aroylnitrenes. Each of the azides studied is a derivative of benzoyl azide containing an acyl group to act as an internal triplet sensitizer and an additional functional group useful for linking the azide to a site-selecting probe molecule. The findings show that benzoyl azides containing the three substituents in a 1,3,5-pattern might be useful for labeling of lipophilic molecules.     

A highly effective cobalt catalyst for olefin aziridination with azides: hydrogen bonding guided catalyst design

[Co(P1)], which was designed on the basis of potential hydrogen-bonding interactions in the metal-nitrene intermediate, is a highly active aziridination catalyst with azides. [Co(P1)] can effectively aziridinate various aromatic olefins with arylsulfonyl azides under mild conditions, forming sulfonylated aziridines in excellent yields. The Co-based system enjoys several attributes associated with the relatively low cost of cobalt and the wide accessibility of arylsulfonyl azides. Furthermore, it generates stable dinitrogen as the only byproduct.     

Synthesis of polysubstituted N-H pyrroles from vinyl azides and 1,3-dicarbonyl compounds

Two synthetic methods for tetra- and trisubstituted N-H pyrroles are presented: (i) the thermal pyrrole formation by the reaction of vinyl azides with 1,3-dicarbonyl compounds via the 1,2-addition of 1,3-dicarbonyl compounds to 2H-azirine intermediates generated in situ from vinyl azides; (ii) the Cu(II)-catalyzed synthesis of pyrroles from alpha-ethoxycarbonyl vinyl azides and ethyl acetoacetate through the 1,4-addition reaction of the acetoacetate to the vinyl azides. By applying these two methods, regioisomeric pyrroles can be prepared selectively starting from the same vinyl azides.     

Ammine Complexes of Na‐, Ag‐, Mn‐, and Zn‐Azides

The synthesis of ammine metal azides is achieved through a simple route in liquid ammonia solution. Azides of silver, sodium, manganese, and zinc were obtained as ammine complexes from liquid ammonia and the solid compounds were characterized. The NH₃ solutions were investigated by means of NMR spectroscopy as well. The triamminesilver(I) azide as well as the unusual tetraamminesilver(I) and pentaamminesodium(I) azides are presented. The structures of the hexaamminemanganese(II) and hexaamminezinc(II) azides, which crystallize with four ammonia molecules of solvation, are elucidated. From these compounds the binary azides Mn(N₃)₂ and Zn(N₃)₂ were obtained by (careful) heating.     

REDUCTION OF AZIDES TO AMINES OR AMIDES WITH ZINC AND AMMONIUM CHLORIDE AS REDUCING AGENT

ABSTRACT

Alkyl azides and acyl azides were reduced to the corresponding amines and amides with zinc and ammonium chloride as reducing agent under mild conditions in good to excellent yield.     

Liquid azide salts and their reactions with common oxidizers IRFNA and N2O4

Several imidazolium-based ionic liquid azides with saturated and unsaturated side chains were prepared, and their physical and structural properties were investigated. The reactivity of these new as well as some previously reported ionic liquid azides with strong oxidizers, N 2O 4 and inhibited, red-fuming-nitric acid (IRFNA), was studied.     

叠氮根电负性的量子化学研究

用ab initio, MINDO/3, MNDO和DV-Xa等量子化学方法计算研究了一些分子型和离子型(碱金属)叠氮化物及相应氯化物的平衡构型和电子结构。结构表明: 在分子型叠氮化物中叠氮根的电负性较氯小、与氮相当; 而在离子型金属叠氮化物中,叠氮根的电负性和氯相当或较氯稍大。将计算所得正则离域分子轨道进行定域化处理, 发现产生这种电负性差异的主要原因是上述两类叠氮化物中N2的成键状况不同, 本文对此进行了较为细致的分析。     

Sulfonyl-PYBOX Ligands Enable Kinetic Resolution of α-Tertiary Azides by CuAAC

We report the first highly selective kinetic resolution of racemic α-chiral azides via Cu-catalyzed azide-alkyne cycloaddition (CuAAC). Newly developed pyridine-bisoxazoline (PYBOX) ligands, bearing a C4 sulfonyl group, enable effective kinetic resolution of racemic azides derived from privileged scaffolds such as indanone, cyclopentenone, and oxindole, and their asymmetric CuAAC to afford α-tertiary 1,2,3-triazoles with high to excellent ee values. DFT calculations and control experiments reveal that the C4 sulfonyl group decreases the Lewis basicity of the ligand and increases the electrophilicity of the copper center for better recognition of azides, and functions as a shielding group to make the chiral pocket of the catalyst more effective.     

Novel approach to the design of potential bioactive alkaloid anabasine conjugates using click chemistry methodology

Anabasine‐containing azides and acetylenes were used as building blocks in copper(I)‐catalyzed 1,3‐dipolar cycloaddition reactions with a series of acetylenes and azides via click methodology to provide a range of anabasine conjugates being potential ligands for neuronal nicotinic acetylcholine receptors.     

Azides in the Synthesis of Various Heterocycles

In this review, we focus on some interesting and recent examples of various applications of organic azides such as their intermolecular or intramolecular, under thermal, catalyzed, or noncatalyzed reaction conditions. The aforementioned reactions in the aim to prepare basic five-, six-, organometallic heterocyclic-membered systems and/or their fused analogs. This review article also provides a report on the developed methods describing the synthesis of various heterocycles from organic azides, especially those reported in recent papers (till 2020). At the outset, this review groups the synthetic methods of organic azides into different categories. Secondly, the review deals with the functionality of the azido group in chemical reactions. This is followed by a major section on the following: (1) the synthetic tools of various heterocycles from the corresponding organic azides by one-pot domino reaction; (2) the utility of the chosen catalysts in the chemoselectivity favoring C−H and C-N bonds; (3) one-pot procedures (i.e., Ugi four-component reaction); (4) nucleophilic addition, such as Aza-Michael addition; (5) cycloaddition reactions, such as [3+2] cycloaddition; (6) mixed addition/cyclization/oxygen; and (7) insertion reaction of C-H amination. The review also includes the synthetic procedures of fused heterocycles, such as quinazoline derivatives and organometal heterocycles (i.e., phosphorus-, boron- and aluminum-containing heterocycles). Due to many references that have dealt with the reactions of azides in heterocyclic synthesis (currently more than 32,000), we selected according to generality and timeliness. This is considered a recent review that focuses on selected interesting examples of various heterocycles from the mechanistic aspects of organic azides.     

Photochemistry of fluorophenyl azides in aniline: Asymmetric fluoroazobenzenes by NH singlet nitrene insertion

Several fluorophenyl azides were photolyzed with aniline at room temperature. Only pentafluoro and 2,6-difluorophenyl azides gave asymmetrical fluoroazobenzenes as the major products. These products were generated by singlet NH insertion reaction with aniline followed by oxidation of the resulting aromatic hydrazine.     

Efficient synthesis of sulfonyl azides from sulfonamides

Triflyl azide serves as an efficient diazo transfer reagent in this first direct synthesis of sulfonyl azides from readily available and stable sulfonamides. The process is experimentally simple, mild, and high-yielding. Sulfonyl azides participate in various catalytic transformations providing rapid access to diversely functionalized sulfonamide derivatives in good yields.     

SnCl4/Sn catalyzed chemoselective reduction of glycopyranosyl azides for the synthesis of diversely functionalized glycopyranosyl chloroacetamides

A method for the chemoselective reduction of glycopyranosyl azides using SnCl₄ and tin metal as the reducing agent followed by in situ chloroacetylation of the synthesized glycopyranosyl amine was developed. This reaction is applicable to diversely functionalized glycopyranosyl azides for the synthesis of glycopyranosyl chloroacetamides.     

A Novel Approach to Functionalization of Aryl Azides through the Generation and Reaction of Organolithium Species Bearing Masked Azides in Flow Microreactors

A novel straightforward method for aryl azides having functional groups based on generation and reactions of aryllithiums bearing a triazene group from polybromoarenes using flow microreactor systems was achieved. The present approach will serve as a powerful method in organolithium chemistry and open a new possibility in the synthesis of polyfunctional organic azides.     

A mild and efficient method for preparation of azides from alcohols using acidic ionic liquid [H-NMP]HSO4

We report here an efficient method for the synthesis and characterization of [H-NMP]HSO₄ and its application as an efficient catalyst and solvent for preparation of azides from corresponding alcohols under mild conditions. This processor showed high chemoselectivity for conversion of various alcohols to their corresponding azides.     

A non-metal catalysed oxidation of primary azides to nitriles at ambient temperature

A novel non-metal catalyzed oxidation of organic azides to nitriles under solvent-free conditions is presented employing catalytic amounts of KI, and DABCO in aq. TBHP at room temperature. This non-metal catalyzed oxidation of azides provides good selectivity as double and triple bonds were not oxidized under the present reaction conditions.