... The organic layer was dried (CaCl,) and concentrated in vacuo and the residue was chro- Foos, Steel, Rizvi, and Fraenkel ... Cooper, J. Am. Chem. SOC., 93,7228 (1971). (6) R. M. Acheson, "An Introduction to the Chemistry of Heterocyclic (7) F. W. Fowler, J. Am. Chem. ...