Solid-state (14)N MAS NMR of ammonium ions as a spy to structural insights for ammonium salts.

The high resolution offered by magic-angle spinning (MAS), when compared to the static condition in solid-state NMR of powders, has been used to full advantage in a (14)N MAS NMR study of some ammonium salts: CH(3)NH(3)Cl, (NH(4))(2)(COO)(2) x H(2)O, (CH(3))(3)(C(6)H(5)CH(2))NCl, (CH(3))(3)(C(6)H(5))NI, [(n-C(4)H(9))(4)N](2)Mo(2)O(7), (NH(4))(2)HPO(4), and NH(4)H(2)PO(4). It is shown that the high-quality (14)N MAS NMR spectra, which can be obtained for these salts, allow determination of the (14)N quadrupole coupling parameters, i.e.

Samarium diiodide-induced intramolecular pinacol coupling of dinitrones: synthesis of cyclic cis-vicinal diamines.

Pinacol coupling of alkyl dinitrones mediated by SmI2 was achieved in the presence of a proton source allowing the synthesis of cyclic vicinal diamines with good cis-selectivity.

Catalytic and enantioselective aza-ene and hetero-Diels-Alder reactions of alkenes and dienes with azodicarboxylates.

Lewis acids such as Cu(OTf)(2), Zn(OTf)(2), Yb(OTf)(3) and Nd(OTf)(3) catalyze the aza-ene reaction of alkenes with azodicarboxylates, giving the allylic amination adducts. The use of bis(2,2,2-trichloroethyl)azodicarboxylate as the amination reagent and Cu(OTf)(2) and Yb(OTf)(3) as the catalysts gave the aza-ene reaction of different alkenes, leading to the corresponding allyl amines in high yields. Chiral copper complexes prepared from Cu(OTf)(2) and chiral bisoxazoline ligands were found to catalyze the enantioselective aza-ene reaction of azodicarboxylates with alkenes and the hetero-Diels-Alder reaction with cyclopentadiene, giving the corresponding aza-ene- and hetero-Diels-Alder adducts, respectively, in good yields and moderate enantioselectivities.

Enantioselective Friedel-Crafts type addition of indoles to nitro-olefins using a chiral hydrogen-bonding catalyst--synthesis of optically active tetrahydro-beta-carbolines.

The enantioselective Friedel-Crafts addition of indoles to nitro-olefins using chiral hydrogen-bonding bis-sulfonamides as the catalysts has been developed. The reactions, in the presence of only 2 mol% catalyst, generally proceed in high yields and with enantioselectivities up to 64% ee, and the enantiomeric excess can be improved to >98% ee by recrystallization. Various synthetic transformations of the Friedel-Crafts adducts are demonstrated: the nitro group can easily be reduced to the corresponding amine and the product obtained can undergo a stereocontrolled Pictet-Spengler cyclization to give, for example, enantiopure tetrahydro-beta-carbolines.

New amine-templated zinc phosphates with a temperature-induced increase of structural dimensionality.

Three new amine-templated zinc phosphates, [C4N2H14][Zn(HPO4)2].H2O, AU-I, [C4N2H14][Zn2(H(0.5)PO4)2(H2PO4)], AU-II, and [C4N2H14][Zn5(H2O)(PO4)4], AU-III, are prepared by hydrothermal synthesis using an organic amine, N,N'-dimethylethylendiamine CH3NHCH2CH2NHCH3, as structure-directing agent.

Two new cobalt-zinc orthophosphate monohydrates: hydrothermal synthesis, crystal structures and thermal investigation.

Two new cobalt zinc orthophosphate hydrates with similar chemical formula, (CoxZn(1-x))3(PO4)2.H2O, but different composition and structure, have been prepared by systematic hydrothermal synthesis from the system nCo(CH3COO)2 : (1 -n)Zn(CH(3)COO)2 : 3.5H3PO4 : 2.

Self-assembly of the octanuclear cluster [Cu8(OH)10(NH2(CH2)2CH3)12]6+ and the one-dimensional N-propylcarbamate-linked coordination polymer {[Cu(O2CNH(CH2)2CH3)(NH2(CH2)2CH3)3](ClO4)}n.

The reaction of Cu(ClO4)2.6-H2O and n-propylamine in methanol gives two high-nuclearity products of well-defined compositions. At amine concentrations greater than seven equivalents compared to copper ion concentration, the system fixes carbon dioxide from air to form the one-dimensional carbamate-bridged coordination polymer, {[Cu(mu2-O,O'-O2CNH(CH2)2CH3)(NH2(CH2)2CH3)3](ClO4)}n ({1-ClO4}n).

Radical addition of nitrones to acrylates mediated by SmI2: asymmetric synthesis of gamma-amino acids employing carbohydrate-based chiral auxiliaries.

Alkyl nitrones possessing N-substituted sugars as chiral auxiliaries were found to effectively undergo an SmI(2)-mediated radical addition to n-butyl acrylate affording gamma-amino acid derivatives with high diastereomeric control.

Preparation of a novel diphosphine-palladium macrocyclic complex possessing a molecular recognition site. Oxidative addition studies.

A disphosphine-palladium(0) complex capable of recognising barbiturates has been prepared. Oxidative addition studies with a barbitiurate:aryl iodide conjugate provided new Pd(ii) complexes where the positioning of the Pd-bound aryl group is controlled by the molecular recognition event.

The first catalytic highly enantioselective alkylation of ketimines--a novel approach to optically active quaternary alpha-amino acids.

A series of novel ketimines with intrinsic protecting group anchoring was synthesized and allowed to react with various silylketene acetals in the presence of 5-10 mol % of a chiral Zn(OTf)(2)-(R,R)-Ph-pybox-aqua complex. The corresponding optically active quaternary alpha-amino acid derivatives were obtained in high yields and with enantioselectivities ranging from 34 % up to 95 % ee. The catalyst was studied by (1)H NMR spectroscopy and X-ray crystallography, and a dynamic equilibrium of two species was identified in solution.

Catalytic asymmetric Mannich reactions of glycine derivatives with imines. A new approach to optically active alpha,beta-diamino acid derivatives.

Imines of glycine alkyl esters react with imines in a diastereo- and highly enantioselective Mannich reaction in the presence of chiral copper(I) complexes as the catalyst to give optically active alpha,beta-diamino acid derivatives. A series of imines of glycine esters derived from glycine and aromatic carbonyl compounds has been screened as substrates for the Mannich reaction with different imines in the presence of various combinations of metal salts and chiral ligands. The benzophenone imine of glycine esters was found to react with N-protected imines in a diastereoselective fashion giving functionalized alpha,beta-diamino acid esters with excellent enantioselectivities.

Organocatalytic asymmetric conjugate addition of nitroalkanes to alpha,beta-unsaturated enones using novel imidazoline catalysts.

A new catalytic enantioselective conjugate addition of nitroalkanes to acyclic alpha,beta-unsaturated enones catalyzed by novel organic catalysts has been developed. A series of chiral amines has been tested as catalysts for the addition of 2-nitropropane to benzylideneacetone, and it is found that a novel imidazoline catalyst, prepared from phenylalanine, can catalyze a highly enantioselective 1,4-addition reaction. The reaction of various acyclic and cyclic nitroalkanes was found to proceed well with enantioselectivities up to 86% ee, and enantiopure products can be obtained by recrystallization.

Synthesis and characterization of the barium oxalates BaC2O4.0.5H2O, alpha-BaC2O4 and beta-BaC2O4.

The synthesis of BaC(2)O(4).0.5H(2)O and its thermal decomposition to alpha-BaC(2)O(4) and beta-BaC(2)O(4) was investigated.

Copper-catalyzed enantioselective Henry reactions of alpha-keto esters: an easy entry to optically active beta-nitro-alpha-hydroxy esters and beta-amino-alpha-hydroxy esters.

The catalytic enantioselective Henry reaction of alpha-keto esters with nitromethane has been developed. The reaction conditions have been optimized by the screening of different chiral Lewis acids, solvents, and bases, and it was found that the copper(II)-tert-butyl bisoxazoline complex in combination with triethylamine catalyzed a highly enantioselective reaction giving optically active beta-nitro-alpha-hydroxy esters in high yields and with excellent enantiomeric excesses. The scope of the reaction is demonstrated by the reaction of a variety of different alpha-keto esters.

On the intermediates in chiral bis(oxazoline)copper(II)-catalyzed enantioselective reactions--experimental and theoretical investigations.

The intermediates in the chiral bis(oxazoline)copper(II)-catalyzed reactions have been investigated by means of experimental and theoretical investigations. It is shown that the absolute configuration of the hetero-Diels-Alder adduct obtained from the reaction of ethyl glyoxylate with 1,3-cyclohexadiene in the presence of the chiral bis(phenyloxazoline)copper(II) is dependent on the solvent. In this case, a linear relationship between the enantiomeric excess (ee) and the dielectric constant of the solvent was observed.

Chiral CO(2)-Synthons via Catalytic Asymmetric Hetero-Diels-Alder Reactions of Ketomalonate and Dienes.

A catalytic enantioselective approach for the formation of chiral CO(2)-synthons is presented. The described methodology is based on the reaction of dienes with diethyl ketomalonate using C(2)-symmetric bisoxazolines as the chiral ligands and copper(II) and zinc(II) as the Lewis acids. For cyclic dienes the reaction proceeds in good yield and with up to 93% ee for 1,3-cyclohexadiene, while for cyclopentadiene the reaction also proceeds well at low temperature, but increasing the temperature leads to a retro-Diels-Alder reaction.

Catalytic Approach for the Formation of Optically Active Allyl alpha-Amino Acids by Addition of Allylic Metal Compounds to alpha-Imino Esters.

A new catalytic enantioselective approach for the formation of allyl alpha-amino acid derivatives by reaction of N-tosyl alpha-imino esters with allyl stannanes and silanes catalyzed by chiral copper(I) complexes has been developed. A series of different BINAP and phosphine-oxazoline (P,N) ligands have, in combination with various Lewis acids, been tested as chiral catalysts for allylation of N-tosyl alpha-imino esters. It has been found that both type of ligands, in combination with copper(I) salts, give highly valuable unsaturated alpha-amino acid derivatives.

Total Synthesis of (R)-Dihydroactinidiolide and (R)-Actinidiolide Using Asymmetric Catalytic Hetero-Diels-Alder Methodology.

The total synthesis of the naturally occurring bicyclic lactones (R)-dihydroactinidiolide and (R)-actinidiolide is presented. The key step in the syntheses is the copper(II)-bisoxazoline-catalyzed hetero-Diels-Alder reaction of a cyclic diene with ethyl glyoxylate giving the hetero-Diels-Alder product in high yield and with very high regio-, diastereo-, and enantioselectivity. The total syntheses proceed via an intermediate, which also has the potential for a series of other natural products.

Catalytic Enantioselective Aza Diels-Alder Reactions of Imino Dienophiles.

1 mol% of catalyst is sufficient: The hetero Diels-Alder reaction of α-imino esters 1 with activated conjugated dienes 2 (R=H, Me) needs only 1 mol% of a 2,2'-bis(diarylphosphanyl)-1,1'-binaphthyl (BINAP) copper(I) complex as the catalyst to generate the adducts 3 in good yields and with enantioselectivities up to 96%. The reaction can also be carried out on gram scale! Tos=H CC H SO ; TMS=Me Si.

Improvement of TADDOLate-TiCl(2)-Catalyzed 1,3-Dipolar Nitrone Cycloaddition Reactions by Substitution of the Oxazolidinone Auxiliary of the Alkene with Succinimide.

A significant improvement of metal-catalyzed asymmetric 1,3-dipolar cycloaddition reactions of acyclic nitrones with alpha,beta-unsaturated carbonyl compounds is described using succinimide as a new auxiliary for the alpha,beta-unsaturated carbonyl moiety. In the absence of a catalyst, N-crotonoylsuccinimide reacts with C,N-diphenylnitrone to give the endo-isoxazolidine, whereas in the presence of 10 mol % TiCl(2)(i-PrO)(2) the exo-product is obtained. Four different TiCl(2)-TADDOLate complexes have been tested as catalysts for the 1,3-dipolar cycloaddition reactions, and the most successful catalyst was applied (5 mol %) in a series of reactions between two different alkenoylsuccinimides and three different nitrones.