Aza-Baylis-Hillman reactions of diisopropyl azodicarboxylate or diethyl azodicarboxylate with acrylates and acrylonitrile

It has been found that in the Baylis-Hillman reactions of DIAD or DEAD with acrylates or acrylonitrile, the Lewis base and solvent can significantly affect the reaction rate. Using DABCO as Lewis base in DMF or THF, the corresponding aza-Baylis-Hillman adducts 2 or 3 can be obtained in moderate to good yields.     

DMEAD: a new dialkyl azodicarboxylate for the Mitsunobu reaction

Di-2-methoxyethyl azodicarboxylate (DMEAD) is prepared in 65% yield in two steps as a crystalline solid. Use of DMEAD in the Mitsunobu reaction of a variety of alcohols with pronucleophiles results in good yields of the products under sufficient stereospecificity of inversion, as conventional diisopropyl azodicarboxylate (DIAD) does. Isolation of the product is, however, much easier with DMEAD than that with DIAD, because the hydrazine produced from DMEAD is highly hydrophilic and is completely separable by a simple extraction into neutral water. Purification of the organic layer, after separation of the other by-product, triphenylphosphane oxide, by filtration, easily provides high purity of the product in a good yield. Concentration of the water layer yields the hydrazine, which can be reused for the preparation of DMEAD. One-step removal of the two by-products by the aqueous extraction was also possible when trimethylphosphane and DMEAD were employed.     

Preparation of carbodiimides by the reaction of thioureas with diethyl azodicarboxylate

A new synthesis of disubstituted carbodiimides from N.N′-disubstituted thioureas, diethyl azodicarboxylate and triphenyl phosphine has been achieved. The intermediates of the reaction have been isolated and found to be 1:1 adducts of the thioureas and diethyl azodicarboxylate, N¹,N²-disubstituted—S—(N³,N⁴-biscarboethoxy)hydrazinoisothioureas which, on treatment with triphenyl phosphine at room temperature, afford the corresponding carbodiimides. Alternatively, the intermediates on heating under reflux in benzene or toluene, decompose to the carbodiimides, diethyl hydrazodicarboxylate and sulphur.     

Separation tagging with cyclodextrin-binding groups: Mitsunobu reactions with bis-(2-(1-adamantyl)ethyl) azodicarboxylate (BadEAD) and bis-(1-adamantylmethyl) azodicarboxylate (BadMAD)

A new method for separation tagging with cyclodextrin-binding groups is introduced and is exemplified in the context of the Mitsunobu reaction with adamantyl tags. HPLC experiments showed that molecules containing adamantyl groups were especially well retained on Sumichiral OA7500 β-methylated cyclodextrin bonded silica columns relative to many other types of molecules. Two new Mitsunobu reagents, bis-(1-adamantylmethyl) azodicarboxylate (BadMAD) and bis-(2-(1-adamantyl)ethyl) azodicarboxylate (BadEAD), were prepared, used in typical Mitsunobu reactions and separated with both β-methylated cyclodextrin bonded silica and standard silica.     

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.     

Formation of silicon centered spirocyclic compounds: reaction of N-heterocyclic stable silylene with benzoylpyridine, diisopropyl azodicarboxylate, and 1,2-diphenylhydrazine

Three silicon centered spirocyclic compounds 1-3, possessing silicon fused six- and five-membered rings have been prepared by the reaction of NHSi (L) [L = CH{(C=CH(2))(CMe)(2,6-iPr(2)C(6)H(3)N)(2)}Si] with benzoylpyridine, diisopropyl azodicarboxylate, and 1,2-diphenylhydrazine, respectively, in a 1:1 ratio. The three spirocyclic compounds (1- 3) were obtained by three different pathways. The reaction of L with benzoylpyridine leads to the activation of the pyridine ring, and dearomatization occurred. Treatment of diisopropyl azodicarboxylate with L favors a [1 + 4]- rather than a [1 + 2]-cycloaddition product, and the azo compound was converted to hydrazone derivative. Finally the reaction of 1,2-diphenylhydrazine and L results in the elimination of hydrogen by activating one of the C-H bonds present in the phenyl ring. All three complexes 1- 3 were characterized by single crystal X-ray structural analysis, NMR spectroscopy, EI-MS spectrometry, and elemental analysis. In addition the optimized structures of probable products and possible intermediates were investigated using density functional theory (DFT) calculations.     

Di-p-nitrobenzyl azodicarboxylate (DNAD): an alternative azo-reagent for the Mitsunobu reaction

Di-p-nitrobenzyl azodicarboxylate is prepared in 83.6% yield in two steps as a bright yellow solid, which can be used as an azo-reagent in the Mitsunobu reaction. When a chiral secondary alcohol was used, sufficient configurational inversion of alcohol occurred under Mitsunobu conditions. That the hydrazine produced from DNAD is semisoluble in some solvents such as THF and CH₂Cl₂ makes it separated easily from the reaction mixture just via filtration. Then the recovered hydrazine compound can be re-exposed to oxidant to produce DNAD. Because DNAD is more stable than DIAD at ambient temperatures and allows easy separation, it is a good alternative azo-reagent for the Mitsunobu reaction.     

Oxidation of alcohols to carbonyl compounds with diisopropyl azodicarboxylate catalyzed by nitroxyl radicals

A nitroxyl-radical-catalyzed oxidation of alcohols using diisopropyl azodicarboxylate (DIAD) as the terminal oxidant is reported. A variety of primary and secondary alcohols including aliphatic, benzylic, and allylic alcohols are efficiently oxidized to their corresponding aldehydes and ketones without overoxidation to carboxylic acid. 1,2-Diols are oxidized to hydroxyl ketones or diketones depending on the amount of DIAD used.     

A new application for diethyl azodicarboxylate: efficient and regioselective thiocyanation of aromatics amines

Highly regioselective thiocyanations of indoles, anilines and pyrrole are achieved via an efficient and simple protocol using NH₄SCN and diethyl azodicarboxylate (DEAD) as a mild oxidant.     

Metal catalyzed C(sp(3))-H bond amination of 2-alkyl azaarenes with diethyl azodicarboxylate

Metal-catalyzed direct C(sp(3))-H bond amination of 2-alkyl azaarenes with N[double bond, length as m-dash]N double bonds has been developed, which expands the scope of C(sp(3))-H bond activation reactions and provides a new access to medicinally important azaarene derivatives.     

Solid-phase microextraction coupled with high performance liquid chromatography using on-line diode-array and electrochemical detection for the determination of fenitrothion and its main metabolites in environmental water samples

The aim of this study was to develop a methodology for the analysis of the insecticide fenitrothion and its two main environmental metabolites, fenitrooxon and 3-methyl-4-nitrophenol. For this purpose, a solid-phase microextraction (SPME) method coupled to high performance liquid chromatography (LC) was optimized. Two on-line detectors, diode array (DAD) and direct current amperometrical (DCAD) were used in order to determine sensitivity and selectivity. The effects of the extraction parameters, including exposure and desorption time, pH, temperature, salt concentration and desorption mode on the extraction efficiency were studied. A satisfactory reproducibility for extractions from samples at 20 ppb-level with RSD < 12.5% (n = 10) was obtained. The calibration graphs were linear in the range of 10-1000 microg l(-1) and detection limits for the target compounds were between 1.2 and 11.8 microg l(-1) depending on which detector was used. The method was applied for determining fenitrothion and both its metabolites in river waters which run through forest areas near to aerial application of the pesticide.     

Activation of silylphosphines by diethyl azodicarboxylate: novel silylation of alcohols

A novel activation mode of silylphosphines and an application of that to silylation of alcohols were described. Silylphosphines were found to be instantly activated by means of DEAD and PPTS to form reactive silyl cation equivalents. By using the activated species, silylation of alcohols successfully proceeded under mild acidic condition.     

Dicyclopentyl azodicarboxylate(DCpAD):A new alternative azo-reagent for the Mitsunobu reaction

Dicyciopentyl azodicarboxylate is introduced as a new azo-reagent which can be conveniently prepared in two steps and be used in the Mitsunobu reaction.Though there are no distinct difference of reactivity between DCpAD and DEAD,the former is a more preferable azo-reagent for its stability.     

Facile synthesis of 1,2,4-triazolines via PPh3-triggered reaction of azodicarboxylate with 2-azidoacrylates

A convenient method for the synthesis of 1,2,4-triazolines by triphenylphosphine-triggered reaction of dialkyl azodicarboxylate with 2-azidoacrylates is described. The cascade reaction procedure is general and efficient.     

Novel chiral 1-phosphono-1,3-butadiene for asymmetric hetero Diels-Alder cycloadditions with nitroso and azodicarboxylate dienophiles

Chiral 1-phosphonodienes bearing a bicyclic (R,R)-1,3,2-dioxaphospholane or a (R,R)-1,3,2-diazaphospholidine auxiliary are potent dienes for asymmetric hetero Diels-Alder reactions. Their reactivity towards model nitroso and azodicarboxylate dienophiles has been studied by means of theoretical chemistry at the B3LYP/6-31G∗∗ level. This model, taking solvent effects into account, allowed us to identify parameters governing the stereoselectivity of this reaction. Our study emphasizes a synergy effect when increasing the steric hindrance of substituents of both partners. This led us to predict high levels of diastereoselectivity for one diene. Accordingly, we have hereby illustrated a convenient and original synthesis of this diene and its cycloadditions with commercially available nitroso and azodicarboxylate dienophiles.     

A comprehensive study of the solvent effects on the cycloaddition reaction of diethyl azodicarboxylate and ethyl vinyl ether: Efficient implementation of QM and TD‐DFT study

In this work, quantum chemistry calculations performed to study the kinetics and thermodynamic parameters of [2+2] cycloaddition reaction of diethyl azodicarboxylate and ethyl vinyl ether in eighty‐three solvents and gas phase. The solvent effect on the reaction path and electron density of the C2? N6 critical bond as the reaction coordinate at the TS was investigated. Calculated rate constants in various solvents showed that increase in the activation dipole moment accelerates the reaction. Based on the time‐dependent studies, using a conductor like polarizable continuum model solvation model, the solvent effects on the excitation energies of the reactants and transition states (TSs) and the corresponding chemical shifts were analyzed. Finally, some correlations between the rate constant and quantum reactivity indices such as electrophilicity index, chemical hardness, and electronic chemical potential were investigated. © 2014 Wiley Periodicals, Inc.     

Novel synthesis of highly functionalized pyrazolines and pyrazoles by triphenylphosphine-mediated reaction of dialkyl azodicarboxylate with allenic esters

[reaction: see text] Reaction of the Huisgen zwitterion, derived from triphenylphosphine and dialkyl azodicarboxylate, with allenic esters affords highly functionalized pyrazolines and pyrazoles. The crystal structure of pyrazoline derivative 7a showed extensive C-H...O interactions. Pyrazole formation proceeds via a novel nitrogen to carbon migration of the carboalkoxy group.     

Esterification of allylic alcohols with benzoic acid in the presence of diethyl azodicarboxylate and triphenylphosphine

Stereoselectivity of esterification reaction of some allylic alcohols, mainly unsaturated pyranosides, with benzoic acid in the presence of diethyl azodicarboxylate and triphenyl phosphine was investigated. The reaction was found to proceed with inversion, without allylic rearrangement.     

A Parham Cyclization route to the 2,3-dihydro-1H-indazole-1,2-dicarboxylate ring systems via condensation of thermolabile aryllithium reagents and azodicarboxylate esters

The Parham Cyclization reaction of o-lithiobenzyl chlorides (generated by low temperature halogen-metal exchange of the corresponding o-bromobenzyl chlorides with n-butyllithium) with azodicarboxylate esters provides a new entry to the 2,3-dihydro-1H-indazole-1,2-dicarboxylate ring system in moderate to good yield.     

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.