Diisopropyl Azodicarboxylate Research Articles

Fabrications of Electrospun Mesoporous TiO2 Nanofibers with Various Amounts of PVP and Photocatalytic Properties on Methylene Blue (MB) Photodegradation.

The superior chemical and electrical properties of TiO2 are considered to be suitable material for various applications, such as photoelectrodes, photocatalysts, and semiconductor gas sensors; however, it is difficult to commercialize the applications due to their low photoelectric conversion efficiency. Various solutions have been suggested and among them, the increase of active sites through surface modification is one of the most studied methods. A porous nanostructure with a large specific surface area is an attractive solution to increasing active sites, and in the electrospinning process, mesoporous nanofibers can be obtained by controlling the composition of the precursor solution. This study successfully carried out surface modification of TiO2 nanofibers by mixing polyvinylpyrrolidone with different molecular weights and using diisopropyl azodicarboxylate (DIPA). The morphology and crystallographic properties of the TiO2 samples were analyzed using a field emission electron microscope and X-ray diffraction method. The specific surface area and pore properties of the nanofiber samples were compared using the Brunauer-Emmett-Teller method. The TiO2 nanofibers fabricated by the precursor with K-30 polyvinyl pyrrolidone and diisopropyl azodicarboxylate were more porous than the TiO2 nanofibers without them. The modified nanofibers with K-30 and DIPA had a photocatalytic efficiency of 150% compared to TiO2 nanofibers. Their X-ray diffraction patterns revealed anatase peaks. The average crystallite size of the modified nanofibers was calculated to be 6.27-9.27 nm, and the specific surface area was 23.5-27.4 m2/g, which was more than 150% larger than the 17.2 m2/g of ordinary TiO2 nanofibers.

Ultrafast Poly(disulfide) Synthesis in the Presence of Organocatalysts

An organocatalyst-mediated, extremely rapid, robust, and practical poly(disulfide) synthesis method is introduced to polymer chemistry. A variety of organocatalysts were initially screened using commercially available 1,6-hexanedithiol and diisopropyl azodicarboxylate (DIAD) to reveal the best catalyst for the process. Remarkably, although a very low amount of catalyst loading (5%), all the catalysts examined afforded poly(disulfide) in 1 min with low to high molecular weights. Among them, triphenylphosphine was selected as the suitable catalyst after the kinetic measurements and used to determine the optimum conditions for polymerization. Various poly(disulfide)s with molecular weights up to 85.6 kDa could be successfully prepared using optimum conditions. Poly(disulfide) synthesis was also attempted with a “catalyst-free” approach, it was found that a polymer can be prepared under this condition, and its molecular weight increases with increasing temperature. The obtained polymers were characterized using common spectroscopic measurements, and the results revealed that the hydrazine unit derived from DIAD was incorporated into polymer chains as an end-capping agent. Also, a depolymerization study was achieved on a model poly(disulfide) using dithiothreitol as a reducing agent. It is believed the straightforward poly(disulfide) synthesis method comprising mild conditions introduced in this study will be of great interest in synthetic polymer chemistry.

Studies towards DIAD promoted N-demethylation of N,N-dimethylanilines

The demethylation of N,N-dimethylanilines promoted by diisopropyl azodicarboxylate (DIAD) to provide N-methylanilines was achieved in this paper. This protocol featured with mild reaction condition, simple operation and moderate to good yield. The intermediates were isolated and identified by means of spectroscopy methods. The reaction mechanism was investigated experimentally and further verified by theoretical calculations. This method could be applied to the study of the metabolites of medicines containing N,N-dimethylaniline fragments.

Alkylphosphinites as Synthons for Stabilized Carbocations.

We present a new acid-free method for the generation of carbocations based on a redox condensation reaction that enables SN1 reactions with a variety of nucleophiles. We utilize readily synthesized phosphinites that are activated by diisopropyl azodicarboxylate to form betaine structures that collapse upon adding a pronucleophile, thereby yielding reactive carbocation intermediates. We also employ this approach for the alkylation of some bioactive molecules.

Silver‐Mediated Conversion of Alcohols to Carbonates with Dialkylazodicarboxylate

AbstractConversion of alcohols to carbonate was observed under the mild conditions of Mitsunobu reaction in presence of silver salt. An investigation is undertaken to explore this unexpected observation, where the presence of DEAD (Diethylazodicarboxylate) and silver salt is essential, while Ph3P is not required. The formation of carbonate is stereospecific, follows with retention of configuration; iso‐propyl carbonate is formed when DIPAD (Diisopropylazodicarboxylate) is used. The method is extended for several examples of alcohols, while it doesn't works for phenols.

Sunlight‐Mediated Degradation of Polyethylene under the Synergy of Photothermal CH Activation and Modification

AbstractThe reuse of waste plastic has always been one of the challenges in the field of macromolecular science. The authors report that the degradation of polyethylene (PE) plastics can be achieved by a photothermal reaction using tetrabutylammonium decatungstate (TBADT) as photocatalysts, and the grafting of diisopropyl azodicarboxylate (DIAD) onto PE concurrently occurs under sunlight irradiation. Through adjusting the amount of DIAD or TBADT used in the reaction, low molecular weight PE waxes with tunable polarity can be prepared. This method can be applied to different sorts of PE plastics including films, gloves, and bags. Subsequently, synthesized low molecular weight PE‐graft‐DIAD waxes are used as compatibilizers to successfully realize the compatibilized blending of polyolefin plastics and starch, which paved a viable way to reuse waste plastics to reduce environmental pollution.

Highly Selective Mitsunobu Esterification of Cellulose with Hydroxycinnamic Acids

AbstractCellulose esters of hydroxycinnamic acids, namely ferulic‐, p‐coumaric‐, and caffeic acid, are synthesized by Mitsunobu esterification applying triphenylphosphine and diisopropyl azodicarboxylate in N,N‐dimethylacetamide/LiCl. The reaction is found to be highly selective and took place at primary hydroxyl groups at position 6 of cellulose without undesired conversion of double bonds and phenolic hydroxyl groups. Molecular structure characterization is performed by FTIR‐ and NMR spectroscopy. The products are soluble in dimethyl sulfoxide and possessed degree of substitution (DS) values of up to 0.5. DS values are determined by two independent methods, namely 1H NMR spectroscopy of peracetylated derivatives and UV spectroscopy of extracted ferulic acid. The synthesis of cellulose hydroxycinnamates is very important to design lignocellulosic model systems and antioxidative bioinspired materials.

A new “Mitsunobu homocoupling” reaction using aldol adducts of kojic acid

In this study, we attempted to carry out the Mitsunobu 1,4-elimination using the kojic acid analog 3, which carries a hydroxymethyl group on C-6 introduced by aldol condensation, to obtain an effective Michael acceptor 4. To the ethyl acetate solution of 3 and Ph3P, diisopropyl azodicarboxylate was added quickly at 0 °C, resulting in the immediate generation of a yellow precipitate. NMR, mass spectrometry, and X-ray crystal structure analyses allowed to identify the precipitate as a diastereomeric/racemic mixture of dimeric compounds of 4. The dimerization reaction was hypothesized to occur through two major steps: (i) intramolecular dehydration of 3 by Mitsunobu reagents and (ii) homocoupling of the dehydration product 4 to form a new trans-carbon–carbon double bond. Presumably, the enol ether moiety of 4 acts as an electron donor and immediately attacks the α,β-unsaturated carbonyl group of another molecule via a reaction that can be dubbed “Mitsunobu homocoupling.”

Corrigendum: Convergent Total Synthesis of Asimicin via Decarbonylative Radical Dimerization

The reagent used in the conversion of compound 13 to compound 14 was iPrO2CN=NCO2iPr (diisopropyl azodicarboxylate) and not iBuO2CN=NCO2iBu as erroneously written in Scheme 3 and its legend (page 18909) and the Supporting Information (page S15). The authors apologize for the error and for any inconvenience caused.

Development of a continuous process: a perspective for Mitsunobu reaction

The developments around flow processing technology have paved the way for new avenues and perspectives to consider in the field of organic chemistry and engineering. In this study, customized flow equipment was utilized to develop and optimize the Mitsunobu reaction. The flow reactor was a prototype of a simple tubular reactor based on the plug flow reactor concept. The experimentation methodology was designed through the statistical design of experiments approach to minimize the number of experiments. The molar ratios of cyclohexanol (1) and o-cresol (2) and interaction effects of triphenylphosphine, diisopropyl azodicarboxylate were studied in detail. The reaction profile of flow experiments agreed with the batch conditions adding noteworthy improvements to the overall reaction time, selectivity, and yield towards the desired product 1-(cyclohexyloxy)-2-methylbenzene (3). The Mitsunobu reaction in batch condition would take on an average of 3 to 5 h, which was effectively accomplished in 30 to 45 mins in this flow reactor. The generated mathematical model is in good agreement with the reaction conditions. We believe that the process could be executed continuously without a break, readily scaled to kilogram quantities in a short time without further development.

Synthesis and dynamic NMR study of spiroheterocycles containing a 1,2,4-triazolidine moiety

A one-pot synthesis of spiro-heterocyclic systems containing a 1,2,4-triazolidine moiety via 1,3-dipolar cycloaddition reaction of azomethine ylides (generated in situ from α-amino acids and ninhydrin) with diisopropyl azodicarboxylate in 50% aqueous MeOH at room temperature, is described. The structure of a typical product was confirmed by X-ray crystallography. The 1H NMR spectra of diisopropyl 1,3-dioxo-1,3-dihydrospiro[indene-2,3′-[1,2,4]triazolidine]-1′,2′-dicarboxylate exhibited dynamic NMR effects, which were attributed to the fast positional change of the ester groups and their interaction with N–H as well as with methylene protons, and restricted bond rotation of the carbamate groups. The calculated free-energy of activation (ΔG#) for these dynamic processes are 64 ± 2 kJ mol−1 and 55 ± 2 kJ mol−1, respectively.

Thermal decomposition mechanism of diisopropyl azodicarboxylate and its thermal hazard assessment

Thermal decomposition behavior and decomposition mechanism of diisopropyl azodicarboxylate (DIAD) were characterized and analyzed by C80 micro-calorimetery and STA-FTIR-MS system. And thermal hazard of DIAD was assessed by using self-accelerating decomposition temperature (SADT) as the evaluation index. The results show that only one exothermic peak appeared in decomposition process, and that the onset temperature and peak temperature increase with heating rate, whereas the released reaction heat at the heating rates remained approximately constant at 945.67±23.45 kJ/kg. Based on C80 data, the calculated activation energy of DIAD decomposition ranges from 45 kJ/mol to 77 kJ/mol by Friedman method, while the reaction progress in the range of 0.10–0.90. During thermal decomposition process of DIAD, there is only one stage of weight loss, which starts at about 80 ℃, reaches to the maximum rate of weight loss at 138 ℃, and end up at about 150 ℃. The thermal decomposition mechanism of DIAD can be mainly summarized as the route that the CO single bond breaks at first, then CC breaks, and the NN bond breaks subsequently, then the CO bond or the CN bond breaks, final products such as H2O, CO2 etc. appear from further dissociation and oxidation of molecular ionic fragments at last. According to the above-metioned results, the calculated SADT of DIAD is 89.0 ℃ based on Semenov model, when packed in 25kg standard package.

Deconstructive Functionalization of Ketones via an LMCT-Promoted C–C Cleavage

In this issue of Chem, Zuo and coworkers report an exciting new strategy for the deconstructive functionalization of ketones. Through merging Lewis-acid-catalyzed nucleophilic 1,2-addition and ligand-to-metal charge transfer (LMCT)-promoted C–C cleavage, common strained and unstrained ketones are transformed into synthetically valuable scaffolds with high efficiency under mild conditions.

Nickel(0)-Catalyzed [3+2]-Cycloadditions of Bis(alkylidenecyclopropanes) with Diazenes: A Facile Synthesis of Functionalized ­Pyrazolidine-1,2-dicarboxylates

A nickel(0)-catalyzed intermolecular [3+2] cycloaddition of bis(alkylidenecyclopropanes) with diazenes such as diethyl or diisopropyl azodicarboxylate gave pyrazolidine-1,2-dicarboxylates in moderate to good yields (61–72%).

Cycloadditions of anionic N-heterocyclic carbenes of sydnone imines

Sydnone imines were deprotonated with lithium bis(trimethylsilyl)amide at the C4 position to give the corresponding sydnone imine anions as lithium adducts. These can be represented as lithium stabilized anionic N-heterocyclic carbenes. Treatment with diisopropyl azodicarboxylate (DIAD) gave the corresponding C4 adducts, i.e. 4-hydrazinyl-sydnone imines, which form tautomers in solution. Reductive 1,3-dipolar cycloadditions of the sydnone imine anions with tetracyanoethylene (TCNE) resulted in the formation of pyrazoles, the mechanism of formation of which differs from known reactions. Reaction of the anion derived from the 2-methoxyphenyl sydnone imine with N,N-diisopropylcarbodiimide gave a ring-cleaved bisiminonitrile. Structure elucidations were accomplished by NMR spectroscopy and by four single crystal X-ray analyses.

Rhodium(III)‐Catalyzed ortho‐Alkenylation of Anilides with Maleimides

AbstractA rhodium(III)‐catalyzed ortho‐alkenylation of substituted anilides with maleimides providing 3‐arylated maleimides in good to excellent yields is described. In the reaction, a minor amount of Michael‐type addition product, 3‐arylated succinimides, was also observed. Later, 3‐arylated succinimides was converted into 3‐arylated maleimides in the presence of diisopropyl azodicarboxylate and K2CO3. Generally, a Michael‐type 3‐arylated succinimides was observed in the reaction of maleimides with substituted aromatics via C‐H bond activation. In the present reaction, unusually, a Heck‐type alkenylated product was observed in the major amount. A possible reaction mechanism was proposed and supported by the deuterium labelling studies and computational experiments. The mechanistic investigation and DFT calculations revealed that the time interval for the regeneration of Rh(I) to Rh(III) could be the factor for the observation of a minor ortho alkylated aromatics which was formed via a redox neutral Rh(III) version.

Metal-Oxidant-Free Cobalt-Catalyzed C(sp2)-H Carbonylation of ortho-Arylanilines: An Approach toward Free ( NH)-Phenanthridinones.

A traceless directing group assisted Co-catalyzed C(sp2)-H carbonylation of ortho-arylanilines for the synthesis of free ( NH)-phenanthridinones in metal-based-oxidant-free fashion was accomplished. This protocol employs diisopropyl azodicarboxylate as the CO source and oxygen as the sole oxidant, and provides good yields with various functional tolerance. The methodology has been applied for the total synthesis of PARP inhibitor PJ-34. Furthermore, the kinetic isotopic effect experiments reveal the C-H bond cleavage probably occurred in the rate-determining step.

Stereospecific Allylic Functionalization: The Reactions of Allylboronate Complexes with Electrophiles.

Allylboronic esters react readily with carbonyls and imines (π-electrophiles), but are unreactive toward a range of other electrophiles. By addition of an aryllithium, the corresponding allylboronate complexes display enhanced nucleophilicity, enabling addition to a range of electrophiles (tropylium, benzodithiolylium, activated pyridines, Eschenmoser’s salt, Togni’s reagent, Selectfluor, diisopropyl azodicarboxylate (DIAD), MeSX) in high regio- and stereocontrol. This protocol provides access to key new functionalities, including quaternary stereogenic centers bearing moieties such as fluorine and the trifluoromethyl group. The allylboronate complexes were determined to be 7 to 10 orders of magnitude more reactive than the parent boronic ester.

2‐Arylation/alkylation of benzothiazoles using superparamagneticgraphene oxide‐Fe3O4 hybrid material as a heterogeneous catalystwith diisopropyl azodicarboxylate (DIAD) as an oxidant

In this report, we introduced Graphene oxide‐iron oxide (GO‐Fe3O4) nanocomposites as a heterogeneous catalyst for arylation/alkylation of benzothiazoles with aldehydes and benzylic alcohols in the presence of diisopropyl azodicarboxylate (DIAD) as an oxidant which exclusively produced 2‐aryl (alkyl)‐1H–benzothizoles in moderate to excellent yields. The absence of precious metals and toxic solvent, easy product isolation, and recyclability of the GO‐Fe3O4 with no loss of activity are notable advantages of this method.

Diisopropyl azodicarboxylate mediated selective dehydrogenation of 2-amino-3-cyano 4H-chromenes

Selective dehydrogenation of 2-amino-3-cyano 4H-chromenes to the corresponding 2-iminochromenes mediated by diisopropyl azodicarboxylate under neutral conditions is reported. The dehydrogenation reaction is compatible with phenolic hydroxyl group and generates iminochromene in high yields. The methodology provides an easy access to coumarin and N-tosyl 2-amino-3-cyano-4-aryl 4H-chromenes.