Short Intramolecular Contacts Research Articles

Crystal structures of ten phosphane chalcogenide complexes of gold(III) chloride and bromide.

The structures of ten phosphane chalcogenide complexes of gold(III) halides, with general formula R 1 3-n R 2 nPEAuX 3 (R 1 = t-butyl; R 2 = i-propyl; n = 0 to 3; E = S or Se; X = Cl or Br) are presented. The eight possible chlorido derivatives are: 9a, n = 3, E = S; 10a, n = 2, E = S; 11a, n = 1, E = S; 12a, n = 0, E = S; 13a, n = 3, E = Se; 14a, n = 2, E = Se; 15a, n = 1, E = Se; and 16a, n = 0, E = Se, and the corresponding bromido derivatives are 9b-16b in the same order. Structures were obtained for 9a, 10a (and a second polymorph 10aa), 11a (and its deutero-chloro-form monosolvate 11aa), 12a (as its di-chloro-methane monosolvate), 14a, 15a (as its deutero-chloro-form monosolvate 15aa, in which the solvent mol-ecule is disordered over two positions), 9b, 11b, 13b and 15b. The structures of 11a, 15a, 11b and 15b form an isotypic set, and those of compounds 10aa and 14a form an isotypic pair. All structures have Z' = 1. The gold(III) centres show square-planar coordination geometry and the chalcogenide atoms show approximately tetra-hedral angles (except for the very wide angle in 12a, probably associated with the bulky t-butyl groups). The bond lengths at the gold atoms are lengthened with respect to the known gold(I) derivatives, and demonstrate a considerable trans influence of S and Se donor atoms on a trans Au-Cl bond. Each compound with an isopropyl group shows a short intra-molecular contact of the type C-Hmethine⋯Xcis; these may be regarded as intra-molecular 'weak' hydrogen bonds, and they determine the orientation of the AuX 3 groups. The mol-ecular packing is analysed in terms of various short contacts such as weak hydrogen bonds C-H⋯X and contacts between the heavier atoms, such as X⋯X (9a, 10aa, 11aa, 15aa and 9b), S⋯S (10aa, 11a and 12a) and S⋯Cl (10a). The packing of the polymorphs 10a and 10aa is thus quite different. The solvent mol-ecules take part in C-H⋯Cl hydrogen bonds; for 15aa, a disordered solvent region at z ≃ 0 is observed. Structure 13b involves unusual inversion-symmetric dimers with Se⋯Au and Se⋯Br contacts, further connected by Br⋯Br contacts.

Crystal structures of sixteen phosphane chalcogenide complexes of gold(I) chloride, bromide and iodide.

The structures of 16 phosphane chalcogenide complexes of gold(I) halides, with the general formula R 1 3- nR 2 nPEAuX (R 1 = t-butyl; R 2 = isopropyl; n = 0 to 3; E = S or Se; X = Cl, Br or I), are presented. The eight possible chlorido derivatives are: 1a, n = 3, E = S; 2a, n = 2, E = S; 3a, n = 1, E = S; 4a, n = 0, E = S; 5a, n = 3, E = Se; 6a, n = 2, E = Se; 7a, n = 1, E = Se; and 8a, n = 0, E = Se, and the corresponding bromido derivatives are 1b-8b in the same order. However, 2a and 2b were badly disordered and 8a was not obtained. The iodido derivatives are 2c, 6c and 7c (numbered as for the series a and b). All structures are solvent-free and all have Z' = 1 except for 6b and 6c (Z' = 2). All mol-ecules show the expected linear geometry at gold and approximately tetra-hedral angles P-E-Au. The presence of bulky ligands forces some short intra-molecular contacts, in particular H⋯Au and H⋯E. The Au-E bond lengths have a slight but consistent tendency to be longer when trans to a softer X ligand, and vice versa. The five compounds 1a, 5a, 6a, 1b and 5b form an isotypic set, despite the different alkyl groups in 6a. Compounds 3a/3b, 4b/8b and 6b/6c form isotypic pairs. The crystal packing can be analysed in terms of various types of secondary inter-actions, of which the most frequent are 'weak' hydrogen bonds from methine hydrogen atoms to the halogenido ligands. For the structure type 1a, H⋯X and H⋯E contacts combine to form a layer structure. For 3a/3b, the packing is almost featureless, but can be described in terms of a double-layer structure involving borderline H⋯Cl/Br and H⋯S contacts. In 4a and 4b/8b, which lack methine groups, Cmeth-yl-H⋯X contacts combine to form layer structures. In 7a/7b, short C-H⋯X inter-actions form chains of mol-ecules that are further linked by association of short Au⋯Se contacts to form a layer structure. The packing of compound 6b/6c can conveniently be analysed for each independent mol-ecule separately, because they occupy different regions of the cell. Mol-ecule 1 forms chains in which the mol-ecules are linked by a Cmethine⋯Au contact. The mol-ecules 2 associate via a short Se⋯Se contact and a short H⋯X contact to form a layer structure. The packing of compound 2c can be described in terms of two short Cmethine-H⋯I contacts, which combine to form a corrugated ribbon structure. Compound 7c is the only compound in this paper to feature Au⋯Au contacts, which lead to twofold-symmetric dimers. Apart from this, the packing is almost featureless, consisting of layers with only translation symmetry except for two very borderline Au⋯H contacts.

Inter- and Intramolecular Aryl-Aryl Interactions in Partially Fluorinated Ethylenedioxy-bridged Bisarenes*.

Several ethylenedioxy‐bridged bisarenes with a variety of type and number of aryl groups were synthesized to study non‐covalent dispersion‐driven inter‐ and intramolecular aryl–aryl interactions in the solid state and gas phase. Intramolecular interactions are preferably found in the gas phase. DFT calculations with and without dispersion correction show larger interacting aromatic groups increase the stabilization energy of folded conformers and decrease the intermolecular centroid–centroid distance. Single‐molecule structures generally adopt folded conformations with short intramolecular aryl–aryl contacts. Gas electron diffraction experiments were performed exemplarily for 1‐(pentafluorophenoxy)‐2‐(phenoxy)ethane. A new procedure for structure refinement was developed to deal with the conformational complexity of such molecules. The results are an experimental confirmation of the existence of folded conformations of this molecule with short intramolecular aryl–aryl distances in the gas phase. Solid‐state structures are dominated by stretched structures without intramolecular aryl–aryl interactions but interactions with neighboring molecules.

The crystal structures of two new coumarin derivatives: 2-(4-{2-[(2-oxo-2H-chromen-4-yl)-oxy]acet-yl}piperazin-1-yl)acetamide and N-(2,4-di-meth-oxy-benz-yl)-2-[(2-oxo-2H-chromen-4-yl)-oxy]acetamide.

The title compounds, 2-(4-{2-[(2-oxo-2H-chromen-4-yl)-oxy]acet-yl}piperazin-1-yl)acetamide, C17H19N3O5, (I), and N-(2,4-di-meth-oxy-benz-yl)-2-[(2-oxo-2H-chromen-4-yl)-oxy]acetamide, C20H19NO6, (II), are new coumarin derivatives. In compound (I), the six-membered piperazine adopts a chair conformation. The dihedral angles between the mean planes of the chromene ring and amide plane is 82.65 (7)° in (I) and 26.2 (4)° in (II). The dihedral angles between the mean planes of the chromene ring and the four planar C atoms of the piperazine ring in (I) and the benzene ring in (II) are 87.66 (6) and 65.0 (4)°, respectively. There are short intra-molecular contacts in both mol-ecules forming S(5) ring motifs, viz. N-H⋯N and C-H⋯O in (I), and N-H⋯O and C-H⋯N in (II). In the crystals of both compounds, mol-ecules are linked by N-H⋯O hydrogen bonds, forming chains along [10] in (I) and [010] in (II). The chains are linked by C-H⋯O hydrogen bonds, forming layers parallel to the ab plane in the crystals of both compounds. In the crystal of (I), there are also C-H⋯π and offset π-π inter-actions [inter-centroid distance = 3.691 (1) Å] present within the layers. In the crystal of (II), there are only weak offset π-π inter-actions [inter-centroid distance = 3.981 (6) Å] present within the layers. The inter-molecular contacts in the crystals of both compounds have been analysed using Hirshfeld surface analysis and two-dimensional fingerprint plots.

Crystal structure of tris-(3-methyl-1H-pyrazol-1-yl)methane.

The title mol­ecule, C13H16N6, crystallizes from hexane as a mol­ecular crystal with no strong inter­molecular inter­actions (the shortest C—H⋯N contact is longer than 3.38 Å). A relatively short intra­molecular contact (3.09 Å) has a C—H⋯N angle of 118° which is quite small to be still considered a hydrogen bond. The three pyrazole rings form a propeller-like motif, with one methylpyrazole unit almost perpendicular to the mean plane of the three rings [82.20 (6)°]. The other two methylpyrazole units, with nitrogen donor atoms oriented in opposite directions, are oriented at 67.26 (6) and 72.53 (6)° to the mean plane.

Hydrometallation (M = Al, Ga) of Silicon- and Germanium-centred Oligoalkynes

Abstract Treatment of a variety of alkyl- and arylsilanes, R4-nSi(C≡C-R′)n, and -germanes, R4-nGe(C≡C-R′)n (1-7), with equimolar quantities of the dialkylmetal hydrides HMR″ 2 (M = Al, Ga; R″ = CMe3, CH2CHMe2) yielded by reduction of a single alkynyl group a series of mixed alkenyl-alkynyl compounds R4-nSi(C≡C-R′)n-1{C(MR″2) =CHR′} (n = 2, 3) and R2Ge(C≡C-R′){C[M(CMe3)2]=CHR′} (8-13). Reactions with two equivalents of the hydrides afforded the dialkenyl compounds R2E{C[(M(CMe3)2]=CHR′}2 (E = Si, Ge, 14-17), Ge(C≡C- CMe3)2{C[Ga(CMe3)2]=CH-CMe3}2 (18) and MeSi(C≡C-p-Tol){C[Ga(CMe3)2]=CH-p-Tol}2 (19) [R = Ph, Mes, Me, C6F5; R′ = CMe3, Ph). Most of the products were characterised by Xray crystallography which for the alkenyl-alkynyl derivatives revealed short intramolecular contacts between the coordinatively unsaturated metal atoms and the a-C atoms of unreacted ethynyl groups Cα≡C-R′.

(Cyclopentadienyl)iron(II) Complexes of N-Heterocyclic Carbenes Bearing a Malonate or Imidate Backbone: Synthesis, Structure, and Catalytic Potential in Hydrosilylation

The backbone-functionalized anionic carbenes maloNHC (1R; malonate backbone) and imidNHC (2; imidate backbone) were generated in situ from their respective zwitterionic precursors and treated with FeCp(CO)2I to afford the zwitterionic complexes {FeCp(CO)2(1R)} (3R; 59–84% yield), and {FeCp(CO)2(2)} (4; 77% yield), respectively. Methylation of the malonate complex 3Me takes place at one of the backbone oxygen atoms to give the cationic adduct [FeCp(CO)2(1MeMe)](OTf) ([5Me](OTf); 96% yield), whereas methylation of 4 takes place at the imidate nitrogen atom to produce the cationic adduct [FeCp(CO)2(2Me)](OTf) ([6Me](OTf); 84% yield). All of the complexes were characterized by NMR and IR in solution, while X-ray structure analyses were carried out for 3Me, 4, and [6Me](OTf). In addition, a detailed experimental and theoretical investigation of the electron density within the archetypal zwitterionic complex 3Me was carried out. The observation of short intramolecular contacts between Cipso or Cortho of the mesityl groups of the carbene and the proximal carbonyl groups is rationalized in terms of a noncovalent “through space” π–π* interaction involving a two-electron delocalization of the occupied π(Cipso═Cortho) molecular orbital (MO) of the aryl ring into one vacant π*(C≡O) MO of the carbonyl ligand. A theoretical analysis carried out on dissymmetrical model complexes reveals that the magnitude of such an interaction is correlated with the donor properties of aryl group substituents. A catalyst screening of the above complexes in the hydrosilylation of benzaldehyde under visible light irradiation revealed a dramatic effect of the electronic donor properties of these carbenes on the performances of their complexes, with the more nucleophilic carbene 1tBu– in the zwitterionic species 3tBu appearing as the most efficient. This complex shows good efficiency and excellent chemoselectivity in the hydrosilylation of various aldehydes bearing reactive functional groups. It is also moderately active in the hydrosilylation of a few ketone substrates and exhibits very good performance in the hydrosilylation of representative aldimines and ketimines.

2-(2,3-Dimethylanilino)benzohydrazide

In the title compound, C15H17N3O, the dihedral angle between the benzene rings is 58.05 (9)°. The non-H atoms of the hydrazide group lie in a common plane (r.m.s. deviation = 0.0006 Å) and are close to coplanar with their attached benzene ring [dihedral angle = 8.02 (9)°]. An intra­molecular N—H⋯O hydrogen bond generates an S(6) ring motif in the mol­ecule, and a short intra­molecular contact (H⋯H = 1.88 Å) is also observed. In the crystal, mol­ecules are linked by pairs of N—H⋯N hydrogen bonds into inversion dimers. The crystal packing also features C—H⋯π inter­actions.

Reductive NO dimerization to trans-hyponitrite in diruthenium complexes: Intramolecular attack of hyponitrite on a CO ligand

The reaction of the electronically and coordinatively unsaturated compounds [Ru2(CO)4(μ-H)(μ-PBut2)(μ-L2)] (1) (RuRu) with nitric oxide afforded four new trans-hyponitrito complexes of the general formula [Ru2(CO)4(μ-H)(μ-PBut2)(μ-L2)(μ-η2-ONNO)] (2) in good yields. Thus the complexes 2a–e were obtained using the following bridging biphosphane ligands (μ-L2): dppm (2a, dppm = Ph2PCH2PPh2), dppen (2b, dppen = Ph2PC(CH2)PPh2), dpppha (2c, dpppha = Ph2PN(Ph)PPh2), dpppra (2d, dpppra = Ph2PN(Prn)PPh2), and dppbza (2e, dppbza = Ph2PN(CH2Ph)PPh2). The molecular structures of the complexes 2a–e were determined by X-ray diffraction. Furthermore the molecular structure of the known compound 2a was reinvestigated in light of a better refinement of the short intramolecular contact between the hyponitrite O atom in close vicinity to the C atom of a neighbouring carbonyl group. This unusual effect in crystals of all compounds 2a–e can be interpreted as a nucleophilic intramolecular attack of a hyponitrito ligand towards an electrophilic carbon center of a carbonyl ligand.

Methylc-1-cyano-t-2-methylsulfonyl-3-phenylcyclopropanecarboxylate

The title compound, C13H13NO4S, is a racemic mixture of enanti­omers. Short intra­molecular contacts between sulfonyl O and ester carbonyl C atoms are observed [C⋯O = 2.881 (1), 2.882 (1) and 2.686 (1) Å], indicating the possibility of donor—acceptor inter­actions between these groups. The dihedral angle between the phenyl and cyclopropyl rings is 79.3 (1)°.

Thiosemicarbazone derivatives of nickel and copper: the unprecedented coordination of furan ring in octahedral nickel(ii) and of triphenylphosphine in three-coordinate copper(i) complexes

The influence of substituents at the C(2) carbon of N(1)-substituted thiosemicarbazones, {C(4)H(3)X-C(2)(CH(3))=N(3)-N(2)H-C(1)(=S)N(1)HR(2)} (X = O, S) on the geometry of nickel(ii) complexes has been investigated. The presence of a methyl group at the C(2) position of 2-acetylfuran-N(1)-substituted thiosemicarbazones {(C(4)H(3)O)-C(2)(CH(3))=N(3)-N(2)H-C(1)(=S)N(1)HR(2), R(2) = CH(3), HaftscN-Me; C(2)H(5), HaftscN-Et; C(6)H(5), HaftscN-Ph} induces unusual coordination by the furan ring and yielded high spin octahedral nickel(II) complexes, [Ni(κ(3)-O, N(3), S-aftscN-R(2))(2)], CH(3)1, C(2)H(5)2, and 2[Ni((κ(3)-O, N(3), S-aftscN-Ph)(2)] 3 (μ(eff) = 2.98, 1; 2.96, 2; 2.92, 3). With 2-acetylthiophene-N(1)-substituted thiosemicarbazones, {(C(4)H(3)S)-C(2)(CH(3))=N(3)-N(2)H-C(1)(=S)N(1)HR(2), R(2) = CH(3), HattscN-Me; C(2)H(5), HattscN-Et; C(6)H(5), HattscN-Ph}, N(3), S chelated low spin trans square planar complexes, {[Ni(κ(3)-O, N(3), S-attscN-R(2))(2)], R(2) = CH(3), 4; C(2)H(5), 5; C(6)H(5), 6} with pendant thiophene rings have been obtained. The bigger sized sulfur atoms of the thiophene rings form short intramolecular contacts with the deprotonated hydrazinic nitrogen atoms (SN(2)) inhibiting its lability for possible coordination to nickel(II). Complexes have one independent molecule (1) or two independent molecules (2, 3) in their respective crystal lattices. The simultaneous presence of methyl groups at the C(2) and N(1) atoms of 2-acetylthiophene-N(1)-methylthiosemicarbazone (HattscN-Me) have facilitated the binding of triphenylphosphine in three-coordinate copper(i) halide complexes, [CuX(η(1)-S-HattscN-Me)(Ph(3)P)] (X, Br, 7; Cl, 8), which represent an unusual donor set of ligands, namely, triphenylphosphine, sulfur of a thio-ligand and a halide.

Alternated Quinoid/Aromatic Units in Terthiophenes Building Blocks for Electroactive Narrow Band Gap Polymers. Extended Spectroscopic, Solid State, Electrochemical, and Theoretical Study

We report here the synthesis of three novel pi-conjugated heterocyclic mixed trimers that contain two electron-donating 3,4-ethylenedioxy-2-thienyl (EDOT) units covalently attached to a central proquinoid electron-accepting thienopyrazine moiety (two of these narrow-HOMO-LUMO gap D-A-D compounds also bear hexyl side chains attached either to the outermost alpha positions of the EDOT end rings or to the beta positions of the pyrazine fused ring). The modification of the terthiophene structure upon EDO, pyrazine, and hexyl substitutions has been treated in detail with spectroscopic and theoretical arguments. Solid-state properties reveal the occurrence of short intramolecular contacts between heteroatoms of adjacent rings. The analysis of the structure of the pi-conjugated backbone of each molecule is consistent with a partial quinoid-like pattern which partially reverts to be subtly more aromatic depending on the topology of the positive inductive effect of the hexyl chains. This quinoidization is a consequence of the appearance of a D(EDOT)-->A(PyT)<--D(EDOT) intramolecular charge transfer which further polarizes the structure. The same chemical concepts have been applied to address their electrochemical behavior. The three mixed trimers exhibit amphoteric properties due to the combination of electron acceptor and donor groups. Given their relative low HOMO-LUMO energy gap, these trimers promise to be good candidates for obtaining polymers with significant low energy gap combining electroactivity.

Synthesis and structure of bis-μ-[(methylenedicyclopentanone-2,2′-dioximato)triphenylantimony

The reaction of pentaphenylantimony with methylenedicyclopentanone-2,2′ dioxime affords bis-μ-[(methylenedicyclopentanone-2,2′-dioximato)triphenylntimony] having, according to the X-ray diffraction data, a centrosymmetric structure with two Ph3Sb moieties linked by dioxime bridges. The antimony atom has a distorted trigonal bipyramidal coordination. The Sb-C bond lengths vary in an interval of 2.111(1)–2.137(3) A, and the Sb-O distances are equal to 2.064(1) and 2.0663(9) A. The molecule contains short intramolecular contacts Sb⋅⋅⋅N of 2.876(1) and 2.910(1) A.

Tl(I)-, Cu(I)-, and Ag(I) Complexes of the Ditopic 1,3-Phenylene-Bridged Heteroscorpionate Ligand [1,3-C6H4(tBuBpz2)2]2-

The complexes Tl2[1,3-C6H4(tBuBpz2)2] (1Tl), [Cu(PPh3)]2[1,3-C6H4(tBuBpz2)2] (1Cu), and [Ag(PPh3)]2[1,3-C6H4(tBuBpz2)2] (1Ag) featuring a novel ditopic 1,3-phenylene-bridged heteroscorpionate ligand have been prepared and investigated by 1H, 13C, 11B, and 31P NMR spectroscopy (pz = pyrazolyl). X-ray crystal structure analyses revealed 1Tl and 1Ag to adopt a trans configuration with respect to the phenylene bridge in the solid state. In solution at room temperature, both scorpionate substituents are free to rotate about their B−C(phenylene) bonds. The Tl(I) coordination to two pyrazolyl nitrogen atoms as well as the Ag(I) coordination to two pyrazolyl and one PPh3 ligand is augmented by short intramolecular contacts to the phenylene π-system.

X-ray mapping in heterocyclic design: XI. X-ray diffraction study of 1-benzoyl-3-(pyridin-2-yl)-thiocarbamide and the product of its reaction with oxidants

The structures of 1-benzoyl-3-(pyridin-2-yl)-thiocarbamide C13H11N3O1S1 (I) and 2-benzoylimino-1,2,4-thiadiazole[2,3-a]pyridine C13H9N3O1S1 (II) are studied by X-ray diffraction. Structures I [a = 5.342(4) A, b = 20.428(5) A, c = 11.784(4) A, β = 90.55(2)°, Z = 4, space group P21/n) and II [a = 6.258(6) A, b = 18.068(14) A, c = 10.185(10) tA, β = 95.45(8)°, Z = 4, space group P21/n) are determined by direct methods and refined to R 1 = 0.0673 and 0.0802, respectively. In structure I, both intramolecular (involving the O atom) and intermolecular (involving the N and S atoms) hydrogen bonds are observed. The latter bonds are responsible for the formation of centrosymmetric molecular dimers. In structure II, a short intramolecular contact (2.168 A) is observed between the S and O atoms.

Vibrational spectra and conformational isomerism of calixarene building blocks: 2-benzylphenol.

The conformations and vibrational spectra of 2-benzylphenol have been analysed within the framework of scaled quantum mechanics. It is shown that the solid-state conformation of the 2-benzylphenol molecule corresponds to one of four potential energy minima predicted by non-empirical quantum chemical calculations for the isolated molecule. In the molten state and in diluted CCl4 solutions of the title compound this conformer coexists with another two spectroscopically detected conformations. The presence of several conformers gives rise to the observation of the corresponding number of vsCH2 and vasCH2 bands in the IR spectra, thus providing experimental evidence of the conformational sensitivity of the vCH2 frequencies. It is shown that vCH2 wavenumbers of different kinds of molecules, containing diphenylmethane fragments, are determined by the dihedral angles between the planes of the aromatic rings and the plane of the connecting methylene bridges, except for the case of short intramolecular contacts with the participation of the methylene protons.

Synthesis and structure of 5,5′,6,6′,7,7′,8,8′-octahydro-1,1′-di(methylthio)-3,3′-biisoquinoline

Title compound, C20H24N2S2, crystallizes in the orthorhombic system, space group Pbca, with cell constants a = 5.1968(5) A, b = 15.6692(11) A, c = 22.3881(11) A , Z = 4, T = 293 K, Dcal = 1.299 g cm−3. The structure was solved by direct methods and refined to R value of 0.0465 for 1566 reflections. Two methylthio-octahydroisoquinoline parts of molecule are related by the center of symmetry and possess the trans conformation. This conformation is more energetically stable than cis but the molecule can rotate about the C(6)–C(6′) central bond at room temperature (molecular mechanics calculations). There is a short intramolecular contact C(5)–H(51) ⋅ ⋅ ⋅ N(1′) in the molecule. The molecules in the crystal form molecular layers parallel to (001) crystallographic plane and the molecular packing is determined by the van der Waals forces only.

4′-{[Benzoyl(4-nitrophenylhydrazono)methyl]sulfonyl}acetanilide

The conformation of the title compound, C22H18N4O6S, is stabilized by a strong resonance-assisted intramolecular hydrogen bond linking the hydrazone moiety and the sulfonyl group. The resulting six-membered ring is practically planar. Short intramolecular contacts link oppositely charged atoms of the sulfonyl and β-carbonyl groups. The crystal packing is influenced by intermolecular hydrogen bonds involving the β-carbonyl O atoms and the N—H bonds of the terminal acet­amide moieties.

1,2-Diphenyl-2-(phenyldiazenyl)-2-tosylethanone, an example of a fungicide containing a sulfonyl group.

The molecule of the title compound, C(27)H(22)N(2)O(3)S, adopts an irregular propeller shape with the tetrahedral C1 atom pivotal. The alpha-azophenyl and alpha-phenyl moieties are approximately coplanar. Electrostatic attraction of the oppositely charged atoms generates several short intramolecular contacts involving the sulfonyl, azo and carbonyl groups. Characteristic bond-length distribution of the central part of the molecule indicates that the Coulombic charge transfer is supplemented by hyperconjugation involving donation of electron density from the azo moiety towards the sulfonyl and carbonyl groups.

3-(Ethoxycarbonyldihydroxymethyl)-2-oxo-1,2-dihydroquinoxaline

The crystal structure of the title compound, ethyl 2,2-di­­hy­droxy-2-(3-oxo-3,4-di­hydro­quinoxalin-2-yl)­acetate, C12H12N2O5, indicates a short intramolecular contact between the N1 atom and a hydroxyl group [2.772 (4) Å]. Two intermolecular hydrogen bonds participate in the molecular packing.