Anna E. Koziol

Carbon Dioxide: A Reagent for the Simultaneous Protection of Nucleophilic Centres and the Activation of Alternative Locations to Electrophilic Attack.

Abstract 2-Pyridone, using the one-pot protection method, is lithiated specifically in the 4-position. In this way, a range of 4-substituted 2-pyridones was prepared. Their orientation of substitution was proved by X-ray analysis

A pentagonal pyramidal lead(II) complex with a short PbCl distance

Pb(DAPSC)(Cl) + NO 3 − cristallise dans le systeme triclinique, groupe despace P1 et sa structure est affinee jusqua R=0,035

Crystal structures of two N-methyltriphenylphosphoranimines: triphenylphosphine-N-methylimine borane, Ph3PN(CH3)BH3 and N,N-dimethylaminotriphenylphosphonium tetrafluoroborate, [Ph3PN(CH3)2]+BF4−

Abstract X-ray crystal structure determinations of two N-methyltriphenylphosphoranimines, Ph3PN(CH3)BH3 (1) and [Ph3PN(CH3)2]+BF4− (2), were carried out to determine the effects of π-bonding between P and N in triphenylphosphoranimines, Ph3Pue5fbNR, as a function of formal chargeon the N atom. Crystals of 1 are monoclinic, space group P2 1 /n with a = 11.370(2), b = 10.507(2), c = 14.360(4) A and β = 91.47(2)° with Z = 4. Bond lengths of interest are: Pue5f8N 1.605(3), Nue5f8B 1.583(5), Nue5f8C 1.456(5), average Pue5f8C(phenyl) 1.805(3) A. Bond angles of interest are: Pue5f8Nue5f8C 124.2(2), Pue5f8Nue5f8B 120.7(2), Cue5f8Nue5f8B 114.6(3), average Cue5f8Pue5f8C 106.8(5), average Cue5f8Pue5f8N of 112.0(5)°. Crystals of 2 are monoclinic, space group P2 1 /c with a = 16.379(3), b = 16.777(2), c = 14.481(2) A and β = 94.41(1)° with Z = 8 (2 molecules per asymmetric unit). Average bond lengths of interest are: Pue5f8N 1.626(4), Pue5f8C(phenyl) 1.795(7), Nue5f8C 1.442(13) A. Average bond angles are: Cue5f8Pue5f8C 109(2), Cue5f8Pue5f8N 110(2), Pue5f8Nue5f8C 123(3), Cue5f8Nue5f8C 112.8(4)°. The longer Pue5f8C distances, the shorter Pue5f8N distance and smaller Cue5f8Pue5f8C angles in 1 compared to 2 are consistent with changes in the s-character around the P atoms.

2,4-Dichloro-3-(dimethylaminomethylene)-1,4-cyclohexadiene-1,5- dicarboxaldehyde: X-ray structure, mndo calculations, and rotational barriers of a stable non-aromatic tautomer of a penta-substituted benzene

Abstract Analogues of the title compound have been prepared; minor alterations in the reaction conditions give a benzenoid isomer 2b of the title compound. Reactions of the title compound were studied, and the structure was confirmed by X-ray crystallography. MNDO calculations give a geometry in agreement with that found, and indicate an energy difference of 13 kcal mol in favour of the benzenoid isomer 2a . Temperature-dependent 13C- and 1H-NMR spectra afforded rotational barriers.

The resolution and absolute configuration by X-ray crystallography of the isomeric octopamines and synephrines

Racemates of the naturally occurring biogenic amines, o-, m-, and p-octopamine and p-synephrine, have been resolved by the preparation of suitable diastereoisomeric salts with antipodes of appropriate organic acids. The circular dichroism (c.d.) curves of (–)-m-octopamine hydrochloride and (–)-m-synephrine hydrochloride were superimposable and of opposite sign to those of the corresponding (–)-p-derivatives. X-Ray crystallography of the (–)-3-bromocamphor-8-sulphonate salt of (–)-p-synephrine confirmed (for the first time by direct means in this series of compounds) that the absolute configuration of (–)-p-synephrine is R. It is concluded from the c.d. data that the absolute configuration of (–)-p-octopamine is also R.

Structural studies of two tetracyclines: 4-dedimethylaminotetracycline hydrate and 6-methylene-5-oxytetracycline hydrochloride

The crystal structures of two tetracycline derivatives, 4-dedimethylaminotetracycline hydrate and 6-methylene-5-oxytetracycline hydrochloride (methacycline·HCl), were determined using X-ray intensity data measured on a diffractometer. The first compound crystallizes with two chemical formula and one water molecule per asymmetric unit. The monoclinic crystal [a=7.174(5),b=12.029(9),c=21.117(15) Å,β=93.16(6)°] shows the space groupP21. Crystals of methacycline hydrochloride are orthorhombic, space groupP212121,a=9.472(1),b=11.921(3),c=18.945(4)Å, with one molecule in the asymmetric unit.

The chemistry of N-substituted benzotriazoles. Part 7. The isomeric composition and mechanism of interconversion of some N-(aminomethyl)benzotriazole derivatives

A variety of N-(dialkylaminomethyl)benzotriazoles are shown by 1H and 13C n.m.r., i.r., and X-ray crystallography to exist solely in the 1-substituted form in the crystalline phase, but as an equilibrium mixture of the 1- and 2-isomers in the liquid, melt, solution and argon matrix phases. The 1- and 2-isomers equilibrate by an intermolecular mechanism as proven by cross-over experiments.

Synthesis and structure of an η2-cycloallene complex: carbonyl(η2-cyclohepta-1,2-diene)(η5-cyclopentadienyl)triphenylphosphineiron(II) hexafluorophosphate

The stable η2-cycloallene complex, carbonyl(η2-cyclohepta- 1,2-diene)(η5-cyclopentadienyl)triphenylphosphineiron(II) hexafluorophosphate, was synthesized, permitting the first single crystal X-ray study of the distortions in a cyclic allene transition metal complex.

A caveat. Synthesis and structure of N,N′-propylenebis- (salicylideneiminato)nitrato[O,O]iron(III)

Abstract Crystals of N , N ′-propylenebis(salicylideneiminato)nitrato[ O , O ]iron(III), Fe(salpn)O 2 NO, were obtained from an attempt to prepare crystals of the corresponding dipropylenetriamine complex. The source of the complex is discussed. An X-ray crystal structure study showed that the nitrate ion was bonded to the iron atom in a symmetrical bidentate fashion. The salpn ligand has a non-planar cis -configuration.

Nonbonded interactions. The influence of lone pair repulsions on bond lengths

Nonbonded lone-pair repulsions are postulated as the cause of bond lengthening in isatin and a variety of other small molecules.