Imino Diels-Alder adducts. II. Two pyrano[3,2-c]quinolines
K Ravikumar1, B Sridhar, M Mahesh
1Laboratory of X-ray Crystallography, Indian Institute of Chemical Technology, Hyderabad 500 007, India. ravikumar_iict@yahoo.co.in
Abstract:
8-Chloro-9-fluoro-5-phenyl-3,4,4a,5,6,10b-hexahydro-2H-pyrano[3,2-c]quinoline and 10-chloro-9-fluoro-5-phenyl-3,4,4a,5,6,10b-hexahydro-2H-pyrano[3,2-c]quinoline, both C18H17ClFNO, are diastereoisomers, formed as the result of the imino Diels-Alder reactions of N-benzylideneanilines with 3,4-dihydro-2H-pyran. The crystal structures reveal the stereochemistry of the pyran ring, which is endo/exo to the quinoline ring system formed in the cycloaddition step. In both structures, the pyran ring adopts a chair conformation, while the nitrogen-containing heterocyclic ring prefers a half-chair conformation. The structures differ essentially in the relative orientation of the ring junction H atoms.
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