... J. Heterocyclic Chem., 31, 1513 (1994). ... Chemical ionization mass spectra (ms) were recorded on a Finnegan-MAT TSQ4500 mass spectrometer using isobutane as carrier gas and ... 201°; ir: 1759, 1712 cm-i; Щ-nmr (deuteriochlo- roform): 8 8.16 (d, .1 = 6.3, IH), 6.64 (d, J = 8.1, IH ...