Imino Diels-Alder adducts.: XII.: Two pyrano[3,2-c]quinolines

The crystal structures of pyranoquinolines 9-fluoro-5-phenyl-3,4,4a,5,6,10b-hexahydro-2H-pyrano[3,2-c] quinoline, C18H18FNO, and 9-methyl-5-phenyl-3,4,4a,5,6,10b-hexahydro-2H-pyrano[3,2-c] quinoline, C19H21NO, are isomorphous. In both structures, the pyran ring is exo to the six-membered N-heterocyclic ring formed in the cycloaddition step. The torsion angles across the phenyl linkage for the two structures are. 91.2 (1) and. 88.3 (2)degrees. The striking feature in both crystal packings is that they do not contain the expected conventional hydrogen bonds, in spite of the presence of good hydrogen-bonding functionalities. Possible C-H-...pi interactions are, however, observed.