Melting points were determined in open capillaries on a Thermonik Precision Melting Point cum Boiling Point Apparatus-Model C-PMl3-2 and are uncorrected. Column chromatography and tlc were performed on silica gel (230-400 mesh) and on precoated plates (E. Merck Kieselgel 60 F2%) respectively. IR spectra were recorded using KBr pellets on Perkin-Elmer Infrared 337 spectrophotometer and'H NMR spectra were recorded on a ...