The enantioselective addition of 1-fluoro-1-nitro(phenylsulfonyl)methane to isatin-derived ketimines.

An asymmetric organocatalytic addition of fluorinated phenylsulfonylnitromethane to isatin-derived ketimines was developed. The reaction was efficiently catalyzed by a chiral tertiary amine, cinchonine. This methodology provides a new type of optically active compound with two adjacent quaternary carbon stereocenters in good yield (up to 96%), with moderate diastereoselectivity (up to 5.7 : 1 dr) and excellent enantioselectivity (up to 98/96% ee).

Alkynylation of heterocyclic compounds using hypervalent iodine reagent.

The alkynylation of various nitrogen- and/or sulphur-containing heterocyclic compounds using hypervalent iodine TMS-EBX by utilization of tertiary amines under mild conditions is described. The developed metal-free methodology furnishes the corresponding alkynylated heterocycles bearing quaternary carbon in high yields.

Separation of planar rotamers through intramolecular hydrogen bonding in polysubstituted 5-nitrosopyrimidines.

While purifying new polysubstituted 5-nitrosopyrimidines, the unique separation of pairs of rotamers as chemical species, stabilized by a single intramolecular hydrogen bond and differing only in nitroso group orientation, was achieved. This interesting stereochemical phenomenon is compared to the well-known atropisomerism.

Organocatalytic enantioselective allylic alkylation of MBH carbonates with ß-keto esters.

The highly stereoselective allylic alkylation of Morita-Baylis-Hillman carbonates with ß-ketoesters catalysed by ß-ICD is described. The corresponding products containing two adjacent quaternary and tertiary carbon centers were obtained in good yields with high diastereoselectivity (up to 10 : 1 dr) and enantioselectivity (up to 95% ee).

Production of (+)-globulol needle crystals on the surface mycelium of Quambalaria cyanescens.

The structure of unique colorless needle crystals growing from the surface mycelium of the basidiomycete Quambalaria cyanescens and identified as (+)-globulol was followed by mass spectrometry, X-ray diffraction, and polarimetry. The mechanism of (+)-globulol fragmentation is proposed based on collision induced dissociation mass spectrometry. X-Ray analysis revealed that crystal packing is governed by hydrogen bond O-H.....O connecting the molecules into an infinite helix along a 3-fold screw axis propagating along the longest dimension of the needle crystal (c-axis of the unit cell). The X-ray diffraction data correspond well with the proposed structure determined by mass spectrometry.

Norleucine, a natural occurrence in a novel ergot alkaloid gamma-ergokryptinine.

A novel natural peptide ergot alkaloid gamma-ergokryptinine containing norleucine has been isolated from ergot sclerotia of the field-growing parasitic fungus Claviceps purpurea CCM 8059. Its structure was deduced from the NMR and mass spectral data. The final structural proof was provided by the crystal structure determination, which is the first X-ray structure of a natural Nle-containing secondary metabolite. The conformations of three ergopeptinines: gamma-ergokryptinine, ergoladinine, and alpha-ergokryptinine were compared.

Phosphacarborane chemistry: the 7,8,9,11-, 7,9,8,10- and 7,8,9,10-isomers of nido-P2C2B7H9--diphosphadicarbaborane analogues of 7,8,9,10-C4B7H11.

The reaction between the carborane arachno-4,6-C2B7H13 (1) and PCl3 in dichloromethane in the presence of a "proton sponge" (PS = 1,8-dimethylaminonaphthalene) resulted in the isolation of the eleven-vertex nido-diphosphadicarbaboranes 7,8,9,11-P2C2B7H, (2) and 3-Cl-7,8,11-P2C2B7H, (3-Cl-2) in yields of 54 and 7%, respectively. Replacement of the PS by NEt3 in the same reaction gave diphosphadicarbaboranes 2 and 3-CI-2 together with the isomeric species nido-7,9,8,10-P2C2B7H, (3) in yields of 28, 15 and 3%, respectively. The reaction between the isomeric carborane arachno-4,5-C2B7H13 (4) and PCl3 in dichloromethane in the presence of PS gave the asymmetrical isomer, nido-7,8,9,10-P2C2B7H, (5). along with the chloro derivatives 4-Cl-7,8,9,10-P2C2B7H8 (4-Cl-5) and 11-Cl-7,8,9,10-PC2B7,H8 (11-Cl-5) (yields of 21, 1 and 13%, respectively). The structures of the chlorinated derivatives 3-Cl2 and 11 -Cl-5 were determined by X-ray diffraction analysis. In addition, the structures of all compounds isolated were geometry-optimised and confirmed by comparison of experimental 11B chemical shifts with those calculated by the GIAO-SCF/II//RMP2(fc)/6-31G* method. The calculations also include the structure and 11B NMR shifts of the isomer nido-7,10,8,9-P2C2B7H9 (6) which has not yet been isolated.

(2,6-Bis[(dimethylamino)methyl]-phenyl-N(2),C(1),N(6))diphenyltin(II) bromide monohydrate.

In the title compound, [Sn(C(6)H(5))(2)(C(12)H(19)N(2))]Br.H(2)O, the Sn(IV) atom lies on a twofold axis and is coordinated by a C and two N atoms from the 2,6-bis[(dimethylamino)methyl]phenyl ligand in a tridentate fashion and by two phenyl groups. The resulting geometry is intermediate between square pyramidal and trigonal bipyramidal, with three C atoms in equatorial and the two N atoms in axial positions. The main deformation from ideal trigonal-bipyramidal geometry is seen for the N-Sn-N angle [152.18 (7) degrees]. The Br(-) anion and the water solvate molecule are on an inversion centre and twofold axis, respectively. They form an infinite chain of Br.H-O-H.Br hydrogen bonds [Br.O 3.529 (2) A] without contributing to the primary coordination sphere of the Sn atom.

Ferroelastic n-heptylammonium dihydrogenarsenate.

n-Heptylammonium dihydrogenarsenate, (C(7)H(18)N)[As(O)(2)(OH)(2)] (C7ADA), is ferroelastic at room temperature and isostructural with n-heptylammonium dihydrogenphosphate (C7ADP). In contrast to the other known n-alkylammonium dihydrogenphosphates (CnADP) and dihydrogenarsenates (CnADA), two independent anions in the present structure are substantially disordered ( approximately 88 and approximately 12%, respectively). There are strong hydrogen bonds between the dihydrogenarsenates themselves, and moderate hydrogen bonds between the dihydrogenarsenates and the n-alkylammonium groups. The hydrogen-bond distances correspond well to those observed in the dihydrogenphosphates. There are two H atoms in the structure which are involved in asymmetric hydrogen bonds between respective oxygen pairs. These H atoms jump from the donor to the acceptor O atoms during ferroelastic switching.

A ferrocenyl-substituted pseudotitanocene complex

The title compound, (eta(5)-cyclopentadienyl)[(1,2,3,4, 5-eta)-4-ferrocenyl-1,2,5,6-tetrakis(trimethylsilyl)cyclohexa-2, 4-dien-1-yl]titanium(II), [TiFe(C(5)H(5))(2)(C(23)H(42)Si(4))] or [Tieta(5)-C(6)H(2)Fe(eta(5)-C(5)H(4))(eta(5)-C(5)H(5))Si(CH(3))(3 )(4)(eta(5)-C(5)H(5))], possesses two directly linked metallocene units that subtend an angle of 52.9 (1) degrees (defined by the least-squares planes of the directly connected pi-ligands) associated with the steric requirements of the bulky trimethylsilyl substituents. The cyclohexadienyl ligand adopts an envelope conformation; the perpendicular distance of its eta(5)-plane to the Ti atom is 1.512 (1) A.

Ferroelastic structures of n-pentyl-, n- hexyl- and n-nonylammonium dihydrogenphosphate crystals.

This study reports the structure redeterminations of C(5)H(11)NH(3)(+).H(2)PO(4)(-) (n-pentylammonium dihydrogenphosphate, C5ADP), C(6)H(13)NH(3)(+).H(2)PO(4)(-) (n-hexylammonium dihydrogenphosphate, C6ADP) and C(9)H(19)NH(3)(+).H(2)PO(4)(-) (n-nonylammonium dihydrogenphosphate, C9ADP). The structures are monoclinic (P2(1)/n), belonging to the series of previously studied structures C2ADP-C8ADP and C10ADP. The structures exhibit reproducible ferroelastic switching. There are hydrogen bonds between the dihydrogenphosphates and the n-alkylammonium groups. Among them there are two hydrogen bonds with hydrogens which hop from the donor to the acceptor oxygens during the ferroelastic switching. C5ADP as well as C3ADP differ from the other members of the series by packing of the double layers of the dihydrogenphosphates. Moreover, the packing of n-alkylammonium molecules in all these structures depends on the parity of the number of atoms in the n-alkylammonium chains. All the samples contained two domains and their structures were refined as twins.

Reduction of bis

The reduction of symmetric, fully-substituted titanocene dichlorides bearing two pendant omega-alkenyl groups, [TiCl2(eta5-C5Me4R)2], R = CH(Me)CH= CH2 (1a). (CH2)2CH=CH2 (1b) and (CH2)3CH=CH2 (1c), by magnesium in tetrahydrofuran affords bis(cyclopentadienyl)titanacyclopentanes [Ti(IV)[eta1:eta1: eta5:eta5-C5Me4CH(Me)CH(Ti)CH2CH(CH2(Ti))CH(Me)C5Me4]] (2a), [Ti(IV)[eta1:eta1:eta5: eta5-C5Me4(CH2)2CH(Ti)(CH2)2CH(Ti)(CH2)2C5Me4]] (2b) and [Ti(IV)[eta1:eta1:eta5:eta5-C5Me4(CH2)2CH(Ti)CH(Me)CH(Me)CH(Ti)(CH2)2C5Me4]](2c), respectively, as the products of oxidative coupling of the double bonds across a titanocene intermediate. For the case of complex 1c, a product of a double bond isomerisation is obtained owing to a preferred formation of five-membered titanacycles. The reaction of the titanacyclopentanes with PbCl2 recovers starting materials 1a from 2a and 1b from 2b, but complex 2c affords, under the same conditions, an isomer of 1c with a shifted carbon - carbon double bond, [TiCl[eta5-C5Me4(CH2CH2CH=CHMe)]2] (1c'). The titanacycles 2a-c can be opened by HCl to give ansa-titanocene dichlorides ansa-[[eta5:eta5-C5Me4CH(Me)CH2CH2CH(Me)CH(Me)C5Me4]TiCl2] (3a), ansa-[[eta5:eta5-C5Me4(CH2)8C5Me4]TiCl2] (3b), along with a minor product ansa-[[eta5:eta5-C5Me4CH2CH=CH(CH2)5C5Me4]TiCl2] (3b'), and ansa-[[eta5:eta5-CsMe4(CH2)3CH(Me)CH(Me)CH=CHCH2C5Me4]TiCl2] (3c), respectively, with the bridging aliphatic chain consisting of five (3a) and eight (3b, 3b' and 3c) carbon atoms. The course of the acidolysis changes with the nature of the pendant group; while the cyclopentadienyl ring-linking carbon chains in 3a and 3b are fully saturated, compounds 3c and 3b' contain one asymetrically placed carbon-carbon double bond, which evidently arises from the beta-hydrogen elimination that follows the HCl addition.