... 270 or -PMX 60 spectrometers using tetramethylsilane as an internal standard, the chemical shifts being ... 1] JV Metzger, Thiazoles and their Benzo Derivatives in Compre- hensive Heterocyclic Chemistry, Vol 6, AR ... [3] LF Lee, FM Schleppnik and RK Howe, J. Heterocyclic Chem ...