Studies on diazepines. XXII. Synthesis of monocyclic 1,4-dihetero seven-membered ring compounds using thermal valence bond isomerization of tricyclo(4.1.0.02.5)heptane systems.
The 3-azatricyclo [4.1.0.02.5] heptanes (11-14) prepared readily from pyridines via 2-azabicyclo [2.2.0] hexa-5-enes (10) were found to be useful synthons for seven-membered heterocycles. The thermolysis of the compounds (11-13) having an oxygen, a nitrogen, or a sulfur atom in the 7-position resulted in valence bond isomerization with ring opening, giving rise to the corresponding 1, 4-dihetero seven-membered ring compounds, 1, 4-oxazepine (15), 1, 4-diazepine (16), and 1, 4-thiazepine (17) derivatives. The 3-azatricycloheptane (14) having no hetero atom in the 7-position also afforded the azepine derivative (18).
Heating the 3-azatricyclo[4.1.0.02,5]heptanes (2) prepared from pyridine via 2-azabicyclo[2.2.0]hex-5-enes (1) results in ring opening to give the corresponding 1,4-diheteroseven-memberedringcompounds (3).