Bruce E. Wilson

Carbon-13 chemical-shift tensors in single-crystal methoxybenzenes

Using a two-dimensional NMR orientational correlation technique, carbon-13 chemical-shift tensors have been measured in single crystals of 1,4-dimethoxybenzene, 1,3,5-trimethoxybenzene and 1,2,3-trimethoxybenzene. The two-dimensional technique greatly extends the single-crystal method to materials with a much larger number of different carbon-13 resonance lines. The manner of dealing with chemically identical, but magnetically inequivalent carbons in the unit cell is discussed. The X-ray structure of 1,2,3-trimethoxybenzene is reported for the first time, and a redetermination of the X-ray structure for 1,4-dimethoxybenzene is given. The principal values of all carbon-13 chemical-shift tensors in the three molecules and the orientation of their principal axes have been obtained. Using multiple regressional analysis the principal values of the tensors have been discussed in terms of additive substituent effects. Ab initio calculations of the shielding tensors in anisole (methoxybenzene) and benzene were used to calculate substituent effects which agree closely with the parameters obtained from the regressional analysis.

Improved and large-scale synthesis of certain glycosyl cyanides. Synthesis of 2,5-anhydro-5-thio-D-allononitrile.

The first synthesis of 2,5-anhydro-5-thio-D-allononitrile starting with L-lyxose, via a trifluoromethanesulfonic ester intermediate, has been accomplished. Methods have been developed to achieve a large-scale synthesis of 3,4,5,7-tetra-O-acetyl-2,6-anhydro-D-glycero-D-talo-heptononitrile (5). An improved procedure has been developed to synthesize 2,5-anhydro-3,4,6-tri-O-benzoyl-D-gulononitrile (9). The structures of 5 and the thioamide derivative from 9, 2,5-anhydro-3,4,6-tri-O-benzoyl-D-gulonothioamide, were confirmed by X-ray crystallographic analysis.

New proton-ionizable macrocyclic ligands. Synthesis, basicity, reactions, and structures of two aza crown ethers containing the 4-hydroxypyridine unit

Two new reactive aza crown ethers, (1) and (2), containing the 4-hydroxypyridine unit have been prepared and found to be different with respect to pK(H2O) values for H2L+, structures of the hydrates of HL, and complex formation with benzylamine and the benzylammonium ion.