Judith Murray-Rust

1,2-oxazine chemistry—II : The crystal and molecular structure of N-(p-carboxybenzyl)-tetrahydro-1,2-oxazine

Abstract The crystal structure of the title compound has been determined from X-ray diffractometer data by direct methods, and refined by full matrix least squares techniques to R = 0·057 for 1231 reflections. The crystals are monoclinic, space group C2/C, cell dimensions a = 1665, b = 987, c = 1443 pm, β = 107·37° and Z = 8. The conformation of the tetrahydro-1,2-oxazine ring is a chair with the N-substituent equatorial. There is evidence of significantly greater torsional angles around the N and O atoms than around the ring C atoms, showing the ring to be more puckered than cyclohexane. The hydrogen bond is between the acid group on one molecule and the ring nitrogen on its neighbour.

A novel thermal rearrangement of the 2-thiabicyclo[3,1,0]hex-3-ene system. The crystal and molecular structure of ethyl-2,4-dichloro-5-hydroxy-6-methylbenzoate

Abstract Thermal rearrangement of 1,3-dichloro-6-ethoxycarbonyl-2-thiabicyclo[3, 1, 0]hex-3-ene does not follow the anticipated course, but leads instead to ethyl-2,4-dichloro-5-hydroxy-6-methylbenzoate, whose structure has been confirmed by an X-ray crystal structure determination.

Conversion of clavulanic acid into thiadeoxa nuclear analogues

Abstract 1,4-Addition of sulphur nucleophiles to the diene ( 12 ) derived via the pen-2-em ( 5 ) from clavulanic acid provides the thiadeoxa analogues ( 14 – 15 ). X-ray analysis of the ester ( 14 ) shows the thermodynamically stable isomers to have the same relative stereochemistry as clavulanic acid.

Cyclization of γδ-unsaturated sulphenic acids to give thietan 1-oxide derivatives. Crystal structure of rel-(1R,2S,3R,4R)-3-hexyl-2-hydroxymethyl-4-methylthietan 1-oxide

erythro- and threo-2-t-Butylthio-3-vinylnonan-1-ol have been prepared by Claisen rearrangement of the silylketen acetals derived from (E)-non-2-enyl t-butylthioacetate followed by reduction with lithium aluminium hydride. The sulphur function influenced the stereoselectivity of formation of the silylketen acetals which, in turn, determined the ratio of diastereoisomeric products obtained in the rearrangement. Thermolysis of erythro-2-t-butylsulphinyl-3-vinylnonan-l-ol at 140 °C for 5 min gave erythro-1-(hydroxymethyl)-2-vinyloctanesulphenic acid which cyclized spontaneously to a mixture of rel-(1R,2R,3S,4R)- and rel-(1R,2S,3R,4R)-3-hexyl-2-(hydroxymethyl)-4-methylthietan 1-oxide. threo-2-Butylsulphinyl-3-vinylnonan-1-ol under the same conditions gave a mixture of rel-(1R,2R,3R,4R)- and rel-(1R,2S,3S,4R)-3-hexyl-2-(hydroxymethyl)-4-methylthietan 1-oxide. Allocations of configuration to these thietan 1-oxide derivatives based on transition-state considerations have been substantiated by a determination of the crystal structure of the rel-(1R,2S,3R,4R)-isomer and by n.m.r. spectroscopy, which also led to tentative assignments of conformation.

A biogenetically significant cyclization of humulene-4,5-epoxide

Abstract Rearrangement of humulene-4,5-epoxide with boron trifluoride etherate leads to the formation of two tricyclic alcohols the structures of which are closely related to that of africanol; the X -ray structure of the p -bromobenzoate of one of the alcohols is reported.

1-Phenyl-2,3-diazacycl[3,2,2]azine, a new 10-π electron system. Involvement of 3,5-didehydroimidazo[1,5-a]pyridine?

Abstract 3-Ethylthioimidazo[1,5-a]pyridine reacts with butyl lithium followed by benzonitrile to give the new 10-π electron system, 1-phenyl-2,3-diazacycl[3,2,2]azine, possibly via 3,5-didehydroimidazo[1,5-a] pyridine.

The crystal structure of bicyclo [3.3.3]undecane-1,5-diol and the conformation of bicyclo[3.3.3]undecane (manxane)

Abstract The crystal structure of bicyclo [3.3.3]undecane-1,5-diol has been determined. It is monoclinic, P2 1 / c , a = 12.99(2), b = 14.16(2), c = 12.50(1)A,β = 112.42(2)°, with two independent molecules in the asymmetric unit. One of these is disordered, but the other has almost exact C 3h symmetry and its conformation and precise molecular geometry agree well with previous calculations by molecular mechanics. The molecule shows considerable angle strain, having bridge angles in the range 118–121°

An X-ray structural and thermodynamic investigation of the blue and red forms of (C-meso-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetra-azacyclotetradecane)copper(II) perchlorate

Copper(II) forms two products with C-meso-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetra-azacyclotetradecane (L1), a red and a blue complex. The crystal structures of both complexes (as perchlorates) have been determined. The red complex [Monoclinic, space group P21/c, a= 8.47(1), b= 9.26(1), c= 16.61 (2)A, β= 112.3(3)°] has been solved by heavy-atom methods and refined to R= 0.048. It contains tetragonally distorted octahedral coordination for the copper atom (Cu–N 2.02, 2.06; Cu–O 2.59 A). The blue complex [Monoclinic, P21, a= 8.71 (1), b= 15.68(2), c= 9.44(1)A, β= 107.98(2)°] is pseudosymmetric and could not be completely refined (R= 0.22). It is likely that it is also octahedral, the main difference from the red complex being the inversion of the chiral nitrogen atom at N(8). The enthalpy difference between the two complexes has been determined (14.9 kJ mol–1) and compared to the difference in stability constants. Thermodynamic, conductimetric, and spectral data are considered in the light of the likely structures for both complexes.

Photochemistry of ethenobenzocycloheptenones : A Di-π-methane rearrangement of β,γ-unsaturated aryl ketones

Abstract Benzotropones 6 react with dienophiles 7 to give endo -adducts 8 as shown by PMR. Unlike similar ketones which usually undergo 1,3-acyl shifts or oxadi-π-methane rearrangements, these ethenobenzocycloheptenones 8 , on direct or sensitized irradiation, lead to the di-π-methane rearrangement products 1H-benzo[f]cycloprop[cd]-indenones 9 . The structures of the latter were elucidated by the use of Eu(FOD) 3 and X-ray diffraction. Prolonged irradiation of tetrahydrofluorenone 19 a potential 1,3-acyl shift product of ethenobenzocycloheptenones, gave only dienyl aldehyde 21 in low conversion. These results suggest that the chemical pathway chosen in these reactions is dependent on geometrical and electronic factors.

X-Ray crystallographic determination of the conformation of bicyclo[3.3.0]octane and bicyclo[3.2.0]heptane derivatives and evidence for an O ⋯ CO interaction

The crystal structures of (3a), (3b), and (6) have been determined and show that in both ring systems the cyclopentane ring takes up an endo conformation with the substituents pseudo-axial; this gives rise to trans-annular O ⋯ CO interactions, which are also seen in related epoxides.