... Proton magnetic resonance ('H-nmr) were recorded on a Varían XL-200 spectrometer. Chemical shifts are reported in delta units relative to tetramethylsilane. ... Abstr., 106, 213930x (1985); [c] DTW Chu and AK Claiborne, J. Heterocyclic Chem., 24, 1537 (1987). ...