Azodicarboxylate Esters Research Articles

Efficient CuOAc/DMAP/DEAD‐Catalyzed Aerobic Oxidative Synthesis of Quinazolines

AbstractEfficient approaches toward the synthesis of quinazolines and dihydroisoquinolines have been developed through copper‐catalyzed aerobic oxidative dehydrogenation of N‐heterocycles. The dehydrogenation was achieved through copper‐catalyzed aerobic oxidative dehydrogenation and azodicarboxylate esters‐mediated dehydrogenation of amines. Azodicarboxylate esters could be regenerated from copper‐catalyzed dehydrogenation of corresponding hydrazodicarboxylate esters, which made this catalytic dehydrogenation process more efficient and reactive.

Synthesis and Chemistry of 1,2,4,3-Triazaphosphole Derivatives

Abstract: This review describes the progress made during the last fifty years in the synthesis and chemistry of 1,2,4,3 triazaphospholes. This class of compounds has attracted tremendous homogeneous catalysis and interest in molecular materials science. These fascinating phosphorus heterocycles have conjugated π systems with high degrees of aromaticity. 1,2,4,3- Triazaphospholes can be designed through [3+2] cyclocondensation between functionalized hydrazines with phosphonoimidates that allow the incorporation of additional donor substituents into specific positions of the phosphorus heterocycle. In addition, [4+1] cyclocondensation between functionalized amidrazones and active phosphorus reagents is the most synthetically accessible method. The used strategies facilitated synthetic access to a completely new set of triazaphospholes leading to a much broader scope for potential applications. 1,2,4,3-triazaphospholes displayed reactivity towards a variety of reagents. The phosphorus is particularly prone to undergo oxidative 1,1-addition. Protic reagents such as alcohols, phenols, and amines can be added across the P=N bond of 2H-1,2,4,3-triazaphospholes to yield the dihydro-1,2,4,3-triazaphosphole derivatives. 1H- and 2H-1,2,4,3- triazaphospholes reacted with alcohols, ammonia and amines in the presence of sulfur or selenium to form dihydro- 1,2,4,3-triazaphosphole 3-chalcogenides. The appropriate difunctional reagents such as glycols, 2-azido alcohols and phenol with a heterodiene function in the ortho position reacted with 2H-1,2,4,3-triazaphospholes to yield products formed via 1,2-addition on P=N bond. Similar behavior is shown by 2-hydroxyacetophenone and 2- hydroxy-benzophenone. 2H-1,2,4,3-Triazaphospholes reacted with acetylenes to form [3+2] cycloadducts; the latter change to 1,2,3-diazaphospholes. [4+1] Cycloadditions occurred with α-diimines, azodicarboxylic esters, and 1,2-diketones; in the latter two cases, the resulting products dimerize.

Rhenium Tricarbonyl Complexes of Azodicarboxylate Ligands

The excellent π-accepting azodicarboxylic esters adcOR (R = Et, iPr, tBu, Bn (CH2-C6H5) and Ph) and the piperidinyl amide derivative adcpip were used as bridging chelate ligands in dinuclear Re(CO)3 complexes [{Re(CO)3Cl}2(µ-adcOR)] and [{Re(CO)3Cl}2(µ-adcpip)]. From the adcpip ligand the mononuclear derivatives [Re(CO)3Cl(adcpip)] and [Re(CO)3(PPh3)(µ-adcpip)]Cl were also obtained. Optimised geometries from density functional theory (DFT) calculations show syn and anti isomers for the dinuclear fac-Re(CO)3 complexes at slightly different energies but they were not distinguishable from experimental IR or UV-Vis absorption spectroscopy. The electrochemistry of the adc complexes showed reduction potentials slightly below 0.0 V vs. the ferrocene/ferrocenium couple. Attempts to generate the radicals [{Re(CO)3Cl}2(µ-adcOR)]•- failed as they are inherently unstable, losing very probably first the Cl- coligand and then rapidly cleaving one [Re(CO)3] fragment. Consequently, we found signals in EPR very probably due to mononuclear radical complexes [Re(CO)3(solv)(adc)]•. The underlying Cl-→solvent exchange was modelled for the mononuclear [Re(CO)3Cl(adcpip)] using DFT calculations and showed a markedly enhanced Re-Cl labilisation for the reduced compared with the neutral complex. Both the easy reduction with potentials ranging roughly from -0.2 to -0.1 V for the adc ligands and the low-energy NIR absorptions in the 700 to 850 nm range place the adc ligands with their lowest-lying π* orbital being localised on the azo function, amongst comparable bridging chelate N^N coordinating ligands with low-lying π* orbitals of central azo, tetrazine or pyrazine functions. Comparative (TD)DFT-calculations on the Re(CO)3Cl complexes of the adcpip ligand using the quite established basis set and functionals M06-2X/def2TZVP/LANL2DZ/CPCM(THF) and the more advanced TPSSh/def2-TZVP(+def2-ECP for Re)/CPCMC(THF) for single-point calculations with BP86/def2-TZVP(+def2-ECP for Re)/CPCMC(THF) optimised geometries showed a markedly better agreement of the latter with the experimental XRD, IR and UV-Vis absorption data.

Alkylation Reactions of Azodicarboxylate Esters with 4-Alkyl-1,4-Dihydropyridines under Catalyst-Free Conditions.

Introduction of alkyl groups on azodicarboxylate esters is an important method to prepare alkyl amine derivatives. Herein, we report reactions of 4-alkyl-1,4-dihydropyridines as alkylation reagents with di- tert-butyl azodicarboxylate to prepare alkyl amine derivatives under heating conditions. The alkylation reactions via C-C bond cleavage of the dihydropyridines are achieved in the absence of catalysts and additives.

Asymmetric organocatalytic α-amination of 2-oxindoles with bis(2,2,2-trichloroethyl)azo-dicarboxylate

An enantioselective electrophilic amination of 3-substituted-2-oxindoles is reported, using bis(2,2,2-trichloroethyl)azo-dicarboxylate and commercially available Cinchona alkaloid organocatalysts. The best results were obtained in the reaction of 3-aryl substrates, with high to excellent yields (75% to quantitative) and good stereoselectivity (64–77% ee). Facile reductive conversion of the protected 3-hydrazino fragment into the corresponding primary amine was also demonstrated, to expand the synthetic flexibility of asymmetric electrophilic amination with azo-dicarboxylic esters en route to enantioenriched 3-amino-2-oxindoles. The absolute configuration of 3-amino-3-phenyl-2-oxindole was independently established by electronic circular dichroism (ECD), combined with time-dependent density functional theory (TDDFT).

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.

Base-Catalyzed Asymmetric α-Functionalization of 2-(Cyanomethyl)azaarene N-Oxides Leading to Quaternary Stereocenters.

A simple, new strategy for the direct asymmetric α-functionalization of 2-alkyl azaarenes is described. Specifically, a Brønsted base catalyzed conjugate addition of substituted 2-cyanomethylpyridine (and pyrazine) N-oxides to acrylate equivalents to afford hitherto elusive 2-tert-alkyl azaaryl adducts with high enantioselectivity (up to 94% ee) is realized. Extension of the method to the α-amination reaction by using azodicarboxylate esters as electrophiles is also demonstrated. Key for success is the N-oxide functionality of substrates that acts as a removable activating and stereodirecting group. A bifunctional Brønsted base catalyst bearing a squaramide with an attached bulky silyl group is also disclosed.

Visible light-mediated decarboxylative amination of indoline-2-carboxylic acids catalyzed by Rose Bengal

A visible-light-induced decarboxylative amination of N-protected indoline-2-carboxylic acids and azodicarboxylate esters catalyzed by Rose Bengal has been developed.

Reduction and Hydrogenation of a Diazene by a (β‐Diketiminato)nickel Hydrazide

AbstractA (β‐diketiminato)nickel(II) hydrazido(1–) complex [LtBuNi(η2‐N2H3)], {1, LtBu = [HC(CtBuNC6H3{iPr}2)2]–} has been obtained by treatment of [LtBuNiBr] with hydrazine. In a reaction of 1 with two equivalents of the azo compound diisopropyl azodicarboxylic ester (adc–OiPr) the Ni(N2H3) entity acts as both a hydrogenating and a reducing agent: diisopropyl hydrazidodicarboxylate (hdc–OiPr) is formed, and more adc–OiPr is reduced by two electrons. The resulting (adc–OiPr)2– is found as a ligand in the ultimate nickel product complex, the trinuclear nickel(II) compound [LtBuNi(μ‐adc–OiPr)Ni(μ‐adc–OiPr)NiLtBu] (2), in which two LtBuNi+ units are linked by a [NiII(adc–OiPr)2]2– moiety. The hypothesis that LtBuNiI species are acting as intermediates was supported by the independent finding that 2 can also be obtained by reaction of [LtBuNi(OEt2)] with adc–OiPr.

Synthesis of α‐Hydrazino Ketones via Regio‐ and Stereoselective Electrophilic Amination of Manganese Enolates and Enamines.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of α-Hydrazino Ketones via Regio- and Stereoselective Electrophilic Amination of Manganese Enolates and Enamines

A straightforward procedure for the regio- and stereoselective synthesis of alpha-hydrazino ketones is described. Manganese enolates and manganese enamines derived from ketones and from the corresponding N-sulfinylimines react with azodicarboxylate esters (DTBAD and DEAD) in a regioselective fashion to afford in good to excellent yields the kinetic alpha-hydrazino ketones as sole or highly prevalent products. When enantiopure N-sulfinyl manganese enamines were used the stereoselectivity of these reactions ranged from 40% to 68% ee.

Reactions of N‐Vinylic Phosphazenes with Azodicarboxylic and Acetylenic Esters.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Reactions of N-vinylic phosphazenes with azodicarboxylic and acetylenic esters

N-Vinylic phosphazenes react as enamines (1,4-addition) with azodicarboxylic esters, whereas different behavior is observed when these phosphazenes react with dimethyl acetylenedicarboxylate (3,4-addition). A [2+2] cycloaddition reaction of the vinyl moiety of vinylic phosphazenes with the acetylenic triple bond of the acetylenic esters followed by a ring opening leads to the formation of functionalized conjugated phosphazenes.

A facile preparation of α-hydrazino-α,β-unsaturated ketones via aza-Baylis-Hillman reaction

α-( N, N′-Bisalkoxycarbonyl)hydrazino-α,β-unsaturated ketones are readily prepared via the aza-Baylis-Hillman reaction of alkyl vinyl ketones and azodicarboxylate esters.

Hexahydropyridazine derivatives. 3. Synthesis of hexahydro-4-pyridazinones

The reaction of azodicarboxylic acid esters with 2-methoxy- or 2-trimethylsilyloxy-1,3-butadienes gave a number of 1,2-bis(alkoxycarbonyl)-4-methoxy(trimethylsilyloxy)-1,2,3,6-tetrahydropyridazines, which were hydrolyzed to the corresponding hexahydro-4-pyridazinones.

Detection of electron paramagnetic resonance signals from three different isotope combinations 63Cu/63Cu, 63Cu/65Cu and 65Cu/65Cu in stable dicopper(I) radical complexes

The new stable paramagnetic cations [(R′R2P)2Cu(adcOR″)Cu(PR2R′)2]+, adcOR″= azodicarboxylic ester, have been characterized by high-resolution EPR spectroscopy. Two equivalent copper centres within one molecule give rise to isotope combinations 63Cu/63Cu (47.9%), 63Cu/65Cu (42.6%) and 65Cu/65Cu (9.5%); both isotopes have I= 3/2, but the nuclear magnetic moment is 7.1% higher for 65Cu. A theoretical analysis of the hyperfine splitting pattern, including a stick spectrum and actual computer simulations, is given, and experimental spectra could be successfully reproduced in this way. Factors favouring the detection of individual isotope combination lines, particularly in the outer spectral regions, are the small number of coupling nuclei (14N, 31P) in the ligands, the rather narrow EPR lines of these ligand-centred radical complexes and the relatively large isotropic copper coupling constants of ca. 1.6 mT.

Novel reactions with hetaryldieneamines as activated olefins

In the presence of appropriate reagents, hetaryldieneamines were found to react with only one of their two double bonds. Reaction with aryldiazonium salts resulted in hydrazone2 while azodicarboxylic ester afforded substitution product3. In reactions with benzofuroxan and arylazides, hetaryldieneamines reacted as enamines to yield quinoxaline (4) andv-triazole derivatives (5), respectively.

The asymmetric synthesis of α-amino and α-hydrazino acid derivatives via the stereoselective amination of chiral enolates with azodicarboxylate esters

The utility of azodicarboxylate esters as (+)NH 2 and (+)NH-NH 2 synthons in highly diastereoselective reactions with chiral carboximide-derived enolates has been demonstrated. The lithium enolates derived from 4-substituted N-acyl 2-oxazolidinones were found to react with di- tert-butyl azodicarboxylate (DBAD) to afford the derived 2-hydrazido carboxylic acid derivatives in yields in excess of 90%. The diastereoselectivities of these reactions ranged from 97% to greater than 99%. The subsequent transformation of these adducts to both α-hydrazino and α-amino acids in enantiomeric purities in excess of 99% is described.

Formula omitted

The esters 1 of N -hydroxy-2-thiopyridone react smoothly at room temperature in a thermal reaction with diethyl azodicarboxylic ester to furnish adducts 2 of a novel structure. Photolysis of these adducts affords a convenient route to the little known tetrazanes 8 . Azo compounds without electron withdrawing groups do not react. The Cookson reagent, however, is so reactive that it gives diacyl derivatives of type 14 .

Cycloaddition of azodicarboxylic acid esters to vinylpyridines

The reaction of methyl or ethyl esters of azodicarboxylic acid with 3-, 4-, 5-, or 6-alkyl-2-vinylpyridines proceeds via the scheme of the diene synthesis with the participation of the pseuodcarbodiene system of vinylpyridines and leads to the formation of 1,2,3,4-tetrahydro-5-azacinnoline derivatives. In addition to these “monoadducts,” 4-[N,N′-bis(methoxycarbonyl)hydrazino] derivatives are formed in large amounts., The structures of all of the reaction products were proved by the IR, UV, PMR, and mass spectra. The possibility of the application of the computational methods of MO perturbation theory for the prediction of the probability of the formation of various regioisomers is demonstrated.