Showing papers by "Thomas A. Hamor published in 1984"

Synthesis and chemistry of 1,3-dihydrotellurolo[3,4-b]quinoxaline and derivatives: crystal and molecular structure of 1,3-dihydro-2,2-di-iodo-2λ4-tellurolo[3,4-b]quinoxaline–2,3-bis(iodomethyl)quinoxaline (1:1)

Abstract: The reaction of 2,3-bis(bromomethyl)quinoxaline with tellurium and sodium iodide (2 h) gave the violet compound 1,3-dihydro-2,2-di-iodo-2λ4-tellurolo[3,4-b]quinoxaline, which may be reduced to 1,3-dihydrotellurolo[3,4-b]quinoxaline (m.p. 158–160 °C). The latter compound readily forms a black 1 : 1 complex with 7,7,8,8-tetracyanoquinodimethane. The u.v., n.m.r., i.r., and mass spectra of the new organotellurium heterocycles are presented and discussed. 2,3-Bis(bromomethyl)quinoxaline also reacts with tellurium and potassium iodide (1 h) to give a yellow material for which elemental analysis, n.m.r., and mass spectroscopy suggest a 1 : 1 adduct of the above di-iodo-complex and 2,3-bis(iodomethyl)quinoxaline. Sodium hydrogentelluride reduces 2,3-bis(bromomethyl)quinoxaline to 2,3-dimethylquinoxaline. The crystal and molecular structure of the 1 : 1 adduct of 1,3-dihydrotelluro[3,4-b]quinoxaline, C10H8l2N2Te, with 2,3-bis(iodomethyl)quinoxaline, C10H8l2N2, has been determined. Crystals of the compound are triclinic, space group P, with a= 7.667(2), b= 11.826(4), c= 13.739(4)A, α= 93.26(3), β= 98.37(2), γ= 83.29(2)°, and Z= 2. Final R= 0.059 for 2 998 observed reflections. The structure consists of discrete molecules of C10H8I2N2Te and C10H8I2N2, a pair of each being linked into centrosymmetric dimers by weak Te ⋯ I linkages. The co-ordination about tellurium is a distorted octahedron with two Te–C bonds [2.14(1)A], two axial Te–I bonds [2.886(2), 2.911 (2)A] and two longer equatorial Te–I bonds trans to Te–C [3.761 (2), 3.788(2)A], the longer contact being to an iodine of the organic di-iodide. Large deviations of bond angle from the ideal octahedral angles occur. A further very weak interaction links the dimers into chains along x. No abnormal features are observed in the organic moieties.

Dynamic stereochemistry of imines and derivatives. Part 16. Conformation and stereodynamics of oxaziridines, nitrones, and imines containing the N-(1-mesitylethyl) or (1-pentamethylphenylethyl) group; a nuclear magnetic resonance and X-ray crystallographic investigation

Abstract: The 1H n.m.r. chemical shift nonequivalence of the ortho-methyl groups in eight title compounds observed at or below ambient temperature is assigned to slow rotation about the aryl–CHMe Bond. The rotational barriers(8–17 kcal mol–1)were evaluated by lineshape analysis and compared with that in 1-mesitylethylamine. The conformation of 3,3-diphenyl-2-(1-mesitylethyl)oxaziridine (1), which shows abnormal ortho-methyl signal positions and a high rotational barrier, has been determined in the solid state by X-ray crystallography.