... spectra were recorded by CNRS Service Central d'Analyse, Vernaison (France) on a Bruker AC 200 spectrometer, and by BICT, Swisttal-Heimerzhcim (Germany) on a Bruker CXP/100 spectrometer; chemical shifts are ... [16] RL Williams and SA Cohen, J. Heterocyclic Chem., 8 ...