Tetra-kis(dimethyl-ammonium) trans-di-chloridobis[5,5'-(pyrazine-2,3-diyl)bis(1H-tetra-zol-1-ido-κN(1))]copper(II).

The title compound, (C(2)H(8)N)(4)[Cu(C(6)H(2)N(10))(2)Cl(2)], consists of an anionic complex which is composed of a Cu(II) ion surrounded by four N atoms from two pyrazine-2,3-diylbis(1H-tetra-zol-1-ide) ligands, and two Cl(-) atoms in a trans-Cl(2)N(4) coordination geometry; the Cu(II) atom lies on a site of symmetry 2/m. The Cu-Cl distance of 2.8719 (5) Šis long due to the Jahn-Teller distortion of the d(9) electron configuration of Cu(II) ion. The tetra-zole and pyrazine rings make an N-C-C-N torsion angle of 38.25 (17)°. The charge of the anionic complex is balanced by four dimethyl-ammonium cations, which inter-act with the anionic complexes via N-H⋯N and N-H⋯Cl hydrogen bonds.

An eight-coordinate vanadium thiolate complex with charge delocalization between V(V)-thiolate and V(IV)-thiyl radical forms.

A six-coordinate oxovanadium(V) thiolate complex and an eight-coordinate non-oxovanadium thiolate complex, [PPh(4)][VO(PS3'')(OCH(3))] (1) and [NEt(4)][V(PS3'')(2)] (2) (PS3'' = P(C(6)H(3)-3-Me(3)Si-2-S)(3)(3-)), respectively, have been isolated and structurally characterized. The former belongs to a limited collection of oxovanadium(V) thiolate complexes. The latter has an unusual coordination number of eight. More importantly, its consensus electronic structure derived from its spectroscopic data should be considered as the resonance forms of V(V)-thiolate and V(IV)-thiyl radical species. This implies that V(IV)-thiyl radical can maintain a stable presence in biological systems.

Enantioselective organocatalytic domino Michael-acetalization-Henry reactions of 2-hydroxynitrostyrene and aldehyde for the synthesis of tetrahydro-6H-benzo[c]chromenones.

Asymmetric domino Michael-acetalization reactions of 2-hydroxynitrostyrene and aldehydes "on water" followed by oxidation providing the cis-3,4-disubstituted dihydrocoumarins with excellent enantioselectivities (up to >99% ee). The variant with glutaraldehyde underwent a highly stereoselective domino Michael-acetalization-Henry reaction to afford the tetrahydro-6H-benzo[c]chromen-6-ones after the subsequent oxidation.

Family of V(III)-tristhiolato complexes relevant to functional models of vanadium nitrogenase: synthesis and electronic structure investigations by means of high-frequency and -field electron paramagnetic resonance coupled to quantum chemical computations.

A series of V(III) complexes of varying coordination number (5, 6, and 7) all containing the PS3 ligand (PS3 = trianion of tris(2-thiophenyl)phosphine and its derivatives with other phenyl substituents) has been prepared and structurally characterized. The complexes have general formula [V(PS3)L(n)](0,-), where n = 1 (from L = Cl(-), 1-Me-Im, N(3)(-)), 2 (from L = 2,2'-bpy; counting each N of the bidentate ligand), and 3 (from L = 1-Me-Im, N(2)H(4)). The complexes have also been investigated by direct current (DC) magnetic susceptibility and high-frequency and -field electron paramagnetic resonance (HFEPR). HFEPR, supported by magnetometry, has provided accurate spin Hamiltonian parameters that describe the S = 1 spin ground state of the complexes. Of particular interest are the zero-field splitting (zfs) parameters which, together with structural data, are the empirical starting point for detailed computational studies. The computational methods included density functional theory (DFT), which was only marginally successful, and more advanced ab initio methods (CASSCF and SORCI). The zfs in these complexes is relatively small in magnitude (|D| approximately 1 cm(-1)) and is the result of multiple, often counteracting, spin-orbit coupling (SOC) and spin-spin coupling (SSC) contributions. The specific origin of each of these contributions is described in detail. The results indicate the level of electronic structure calculation possible for transition metal complexes even with multiple unpaired electrons and highly covalent, heavier atom donor ligands.

Organocatalytic enantioselective domino Michael-aldol condensation of 5-oxoalkanal and alpha,beta-unsaturated aldehydes. Efficient assembly of densely functionalized cyclohexenes.

Organocatalytic Michael reaction of glutaraldehyde and 3-arylpropenal followed by the subsequent intramolecular aldol condensation provided 2-arylcyclohex-3-ene-1,3-dicarbaldehydes. Reactions with the 5-oxohexanal variant afforded the highly functionalized cyclohexenedicarbaldehydes in high diastereoselectivity and high enantioselectivity (>99% ee). Structure of the adduct 3j was confirmed unambiguously by X-ray analysis.

Enantioselective organocatalytic formal [3 + 3]-cycloaddition of alpha,beta-unsaturated aldehydes and application to the asymmetric synthesis of (-)-isopulegol hydrate and (-)-cubebaol.

[reaction: see text] The first highly enantioselective organocatalyzed carbo [3 + 3] cascade cycloaddition of alpha,beta-unsaturated aldehydes is reported. Using this methodology, crotonaldehyde is converted to 6-hydroxy-4-methylcyclohex-1-enecarbaldehyde, which is used in the synthesis of (-)-isopulegol hydrate, (-)-cubebaol, and p-tolualdehyde as well as (-)-6-hydroxy-4-methyl-1-cyclohexene-1-methanol acetate, an intermediate in the total synthesis of lycopodium alkaloid magellanine. Other alpha,beta-unsaturated aldehydes give rise to chiral cyclohexadienes via formal [4 + 2] reactions.

Organocatalytic Enantioselective Michael-Michael-Henry Reaction Cascade. An Entry to Highly Functionalized Hajos-Parrish-Type Ketones with Five to Six Contiguous Stereogenic Centers and Two Quaternary Carbons.

An organocatalytic enantioselective reaction of 2-methylcyclopentane-1,3-dione, nitroalkene, and α,ß-unsaturated aldehyde with the diphenylprolinol catalyst was developed to give the highly functionalized Hajos-Parrish-type ketones with five to six contiguous stereocenters and two quaternary carbon stereogenic centers with high diastereoselectivity and enantioselectivity. The structures of the adducts were unambiguously confirmed by single-crystal X-ray crystallographic analyses of the appropriate products.

Intramolecular Diels-Alder cycloadditions of fulvenes. Application to the kigelinol, neoamphilectane, and kempane skeletons.

A variety of polycyclic ring skeletons (e.g., kigelinol, neoamphilectane, and kempene systems) can be prepared rapidly via intramolecular Diels-Alder cycloadditions (IMDA) of fulvenes. The length of the tethers and the diversity of the substituents on the fulvene core dictate the nature of the IMDA pathway. [reaction: see text]

Efficient and stereodivergent synthesis of deoxyimino sugars.

Both cis- and trans-2-substituted-1,2,3,6-tetrahydro-pyridin-3-ols have been prepared via an aldol condensation-ring-closing metathesis sequence. A stereodivergent synthesis of optionally functionalized deoxyimino sugars was achieved via asymmetric dihydroxylation or epoxidation/nucleophilic substitution of these tetrahydropyridines.

Unprecedented microwave effects on the cycloaddition of fulvenes. A new approach to the construction of polycyclic ring systems.

[reaction: see text] Novel cycloaddition reactions between fulvenes and various alkenes and alkynes are promoted by the use of microwave irradiation. These processes result in the formation of intriguing polycyclic ring systems such as those found in isobarbatene, alcyopterosin, and enokipodin A. Importantly, these reactions do not occur under conventional thermolytic conditions.

Hetero [6+3] cycloaddition of fulvenes with N-alkylidene glycine esters: a facile synthesis of the delavayine and incarvillateine framework.

[reaction: see text] In contrast to the [3+2] or [4+3] cycloaddition of N-metalated azomethine ylides and various alkenes, N-benzylidene glycine ethyl ester reacts with fulvenes to give the hetero [6+3] cycloaddition adducts with high stereoselectivity, constituting an efficient and novel route to [2]pyrindines.

Azadiene Diels-Alder cycloaddition of fulvenes: a facile approach to the [1]pyrindine system.

[reaction: see text] Regioselective and stereoselective inverse-electron-demand Diels-Alder reaction of N-sulfonyl-1-aza-1,3-butadiene with fulvenes are described. The methodology provides an efficient and novel route to tetrahydro-[1]pyrindine systems.

Flux Synthesis of LiAuS and NaAuS: "Chicken-Wire-Like" Layer Formation by Interweaving of (AuS)(n)(n)(-) Threads. Comparison with alpha-HgS and AAuS (A = K, Rb).

From the reaction of Au with alkali metal polysulfide liquids, LiAuS and NaAuS were discovered. Orange crystals of LiAuS crystallize in the monoclinic space group C2/c, (no. 15), with a = 8.994(2) Å, b = 8.956(2) Å, c = 7.201(3) Å, beta = 128.68(1) degrees, and Z = 8. Light-yellow planks of NaAuS crystallize in the orthorhombic space group Ccca, (no. 68), with a = 14.658(5) Å, b = 21.043(7) Å, c = 7.118(4) Å, and Z = 32. Both compounds contain infinite one-dimensional (AuS)(n)()(n)()(-) chains, featuring alternating sulfide anions and linear coordinated Au centers. In LiAuS, the chains are zigzag and fully extended and they pack in two mutually perpendicular sets. In NaAuS, the same chains coil in an unusual fashion so that they become interwoven to form layers reminiscent of "chicken-wire". This novel coiling mode allows Au-Au contacts to form, which help to stabilize the structure. The structural relationships between LiAuS, NaAuS, Na(7)Au(5)S(6), AAuQ (A = K, Rb, Cs; Q = S, Se), and alpha-HgS are explored.

One-pot organocatalytic enantioselective domino double-Michael reaction and Pictet-Spengler-lactamization reaction. A facile entry to the "inside yohimbane" system with five contiguous stereogenic centers.

An expedited method was developed for the enantioselective synthesis of dodecahydrobenz[a]indolo[3,2-h]quinolizine containing five contiguous stereogenic centers with high enantioselectivities (>99% ee). The methodology comprises a domino organocatalytic double Michael reaction and Pictet-Spengler-lactamization reaction. The structures and absolute configurations of the appropriate products were confirmed by X-ray analysis.

Organocatalytic Michael-Knoevenagel-hetero-Diels-Alder reactions: an efficient asymmetric one-pot strategy to isochromene pyrimidinedione derivatives.

Synthesis of isochromene pyrimidinedione derivatives having five stereocenters has been achieved by a one-pot Michael-Knoevenagel condensation-inverse-electron-demand hetero-Diels-Alder reaction of α, ß-unsaturated aldehydes, olefinic nitroalkanes, and 1,3-dimethylbarbituric acid via a one-pot strategy with excellent diastereo- and enantioselectivities (up to 99% ee). The structures and absolute configurations of the products were confirmed by X-ray analysis.

Organocatalyzed Michael-Henry reactions: enantioselective synthesis of cyclopentanecarbaldehydes via the dienamine organocatalysis of a succinaldehyde surrogate.

Asymmetric formal [3+2] cycloadditions of 4-hydroxybut-2-enal, a succinaldehyde surrogate, and nitroalkenes with an organocatalyst provided cyclopentanecarbaldehydes containing four consecutive stereogenic centers with excellent enantioselectivities.

Organocatalytic asymmetric anti-selective Michael reactions of aldehydes and the sequential reduction/lactonization/Pauson-Khand reaction for the enantioselective synthesis of highly functionalized hydropentalenes.

A new method has been developed for the enantioselective synthesis of highly functionalized hydropentalenes bearing up to four stereogenic centers with high stereoselectivity (up to 99% ee). This process combines an enantioselective organocatalytic anti-selective Michael addition with a highly efficient one-pot reduction/lactonization/Pauson-Khand reaction sequence. The structures and absolute configurations of the products were confirmed by X-ray analysis.

Enantioselective organocatalytic Michael-Wittig-Michael-Michael reaction: dichotomous construction of pentasubstituted cyclopentanecarbaldehydes and pentasubstituted cyclohexanecarbaldehydes.

Michael addition of carbethoxymethylenetriphenylphosphorane (a Wittig reagent) to nitroalkenes, followed by a reaction with ethyl formylformate and cinnamaldehydes, or formaldehyde and cinnamaldehydes, provided the respective pentasubstituted cyclopentanecarbaldehydes bearing a quaternary carbon center and pentasubstituted cyclohexanecarbaldehydes having five contiguous stereocenters with excellent enantioselectivities (up to >99% ee).

Dynamic kinetic asymmetric synthesis of five contiguous stereogenic centers by sequential organocatalytic stetter and Michael-aldol reaction: enantioselective synthesis of fully substituted cyclopentanols bearing a quaternary stereocenter.

A synthesis of fully substituted cyclopentanes bearing a quaternary carbon center and five contiguous stereogenic centers has been achieved by sequential organocatalyzed Stetter and Michael-Aldol reactions of heteroaromatic aldehydes, nitroalkenes, and α,ß-unsaturated aldehydes via the [1 + 2 + 2] annulation strategy with dynamic kinetic asymmetric transformation and excellent enantioselectivities (up to >99% ee).

Enantioselective total synthesis of (+)-conicol via cascade three-component organocatalysis.

The first asymmetric total synthesis of (+)-conicol has been achieved via a key step reaction involving the organocatalytic domino oxa-Michael-Michael-Michael-aldol condensation of 2-((E)-2-nitrovinyl)benzene-1,4-diol and alpha,beta-unsaturated aldehydes. Structures of the three-component domino reaction adducts, 20 and 21, including their absolute configurations, were confirmed unambiguously by X-ray analysis. Through this work, the absolute configuration of (+)-conicol was thereby elucidated.