Gerald B. Ansell

Intramolecular reactions of nitro-olefin–cyclohexane-1,3-dione Michael adducts. Crystal structure of 3-(4-bromophenyl)-6,7-dihydro-2-hydroxyiminobenzofuran-4(5H)-one

Cyclohexane-1,3-dione and its 5,5-dimethyl derivative (dimedone), in contrast to other β-diketones, behave abnormally in Michael additions to nitro-olefins. From nitro-olefins RCHCH·NO2(R = alkyl or aryl, not H) 3-substituted 6,7-dihydro-2-hydroxyiminobenzofuran-4(5H)-ones can be prepared. These compounds are the first known butenolide derivatives having a 2-hydroxyimino-substituent. 3-(4-Bromophenyl)-6,7-dihydro-2-hydroxyiminobenzofuran-4(5H)-one has been prepared from cyclohexane-1,3-dione and 4-bromo-β-nitrostyrene and resolved into pure syn- and anti-forms. The structures of both forms have been established from n.m.r. spectra, and by X-ray crystallography from diffractometer data. Single crystals of a 1 : 2 mixture of syn- and anti-forms (VIIA and B; anti: syn= 2 : 1) are orthorhombic with space-group Pbca, cell dimensions a= 17·37, b= 7·89, and c= 19·76 A. The crystals were found to be disordered because they contain a mixture of syn- and anti-forms of the oxime. Three possible ways of describing the mixture of syn- and anti-forms were refined by full-matrix least-squares of 805 statistically significant reflections to weighted R values of 0·051, 0·056, and 0·073. None of the three refinements gave good agreement with bond distances previously reported for CN an N–OH in oxime structures (although mean values for the 0·051 and 0·057 refinements did). The observed apparent planarity of the cyclohexenone ring is attributed to the presence of equal amounts of both ring-inversion isomers in the crystalline state. Short intermolecular distances of 2·63 and 2·84 A between the oxygen of both syn- and anti-oxime groups and the ketonic oxygens give strong evidence for intermolecular hydrogen bonding.

Crystal structure of a 1 : 1 complex between silver iodide and morpholine

Crystals of the 1 : 1 complex between silver iodide and morpholine (AgI, C4H9NO) are monoclinic, a= 18.14 ± 0.03, b= 4.528 ± 0.010, c= 9.180 ± 0.020 A, β= 95.9 ± 0.10, space group C2, Z= 4. The structure was solved by use of diffractometer data by the heavy-atom method and refined by full-matrix least-squares to R′ 0.048 for 311 independent reflections. The structure has bands of coplanar iodide ions running parallel to the b axis, arranged within the band at the corners of nearly equilateral triangles. The Ag ions are places alternately above and below successive I3 triangles. Chair-shaped morpholine molecules are attached to the strings by donation of the nitrogen lone-pair to each silver. Along the strings adjacent morpholine molecules are NH ⋯ O bonded to each other.

Formation and crystal structure of 3-(4-bromophenyl)-2-hydroxyimino-6,7-dihydro-4(5H)-benzofuranone. Michael addition of cyclohexane-1,3-dione to 4-bromo-ω-nitrostyrene

The structure of the abnormal Michael adduct named in the title has been established by spectra and X-ray crystallography.

Crystal structure of a complex between silver iodide and piperidine

Crystals of the complex between silver iodide and piperidine (Agl, C5H11N) are orthorhombic, a= 20·220, b= 8·226, and c= 10·240 A, space group Pcna with Z= 8. The intensity data were measured by use of an automatic diffractometer and molybdenum radiation. The structure was refined by full-matrix least-squares methods to wR= 0·039 for 380 statistically significant reflections. The compound consists of tetrahedral clusters of iodide ions with silver ions embedded into the faces of the tetrahedra. There are ‘short’ Ag⋯Ag distances ranging from 2·980–3·095 A within the clusters. The piperidine molecules are linked to the clusters by co-ordination of nitrogen to silver. Hydrogen bonding between the hydrogen atom attached to nitrogen and an iodide ion in an adjacent cluster is possible.

The molecular structure of 1,3-dimethyl-2(3H)-imidazolethione (C5H8N2S)

The crystal structure of the heterocyclic molecule 1,3-dimethyl-2(3H)-imidazolethione and its 1H n.m.r. spectrum have been interpreted as showing partial double-bond character in the N–C–N system, but no aromaticity.

The crystal structure of a complex between silver iodide and piperazine (AgI,½C4N2H10)

An X-ray crystallographic structure determination of the complex between silver iodide and piperazine is reported.

X-Ray crystal structure of hexahydro-1,4-dimethyl-s-tetrazine

The structure of the title compound has been established by X-ray crystallography. Crystals are monoclinic, space group P21/n, Z= 2 and cell dimensions a= 8·996 ± 0·005, b= 8·905 ± 0·005, c= 4·086 ± 0·002 A, β= 95·9 (± 0·1)°. The structure was solved by Patterson and Fourier methods and refined by full-matrix least-squares techniques to R 0·044 for 315 observed reflections. The molecule is centrosymmetric and chair-shaped. N-Methyl groups are equatorial and N-hydrogen atoms axial. All bond lengths agree with previously found values. Each molecule is NH ⋯ N bonded to two others forming strings running parallel to the c axis.

The X-ray structure of 1,4-dimethylhexahydro-s-tetrazine

The structure of 1,4-dimethylhexahydro-s-tetrazine is discussed on the basis of X-ray, n.m.r., and dipole-moment measurements.

The crystal structure of a new 5-tetrazole ylide

One of the products formed by the monoalkylation of sodium 5-dimethylaminotetrazole with 3-chlorobenzyl chloride has been positively identified as an ylide.

The structure of a complex between silver iodide and piperidine (AgI,C5H11N)

An X-ray analysis of the structure of the complex between silver iodide and piperidine has been carried out.