By combination of 1,3-dipolar cycloaddition and N–O single bond insertion, tandem synthesis of dibenzo[1,4]oxazepino[4,5-a]quinolines was accomplished. Reaction of quinoline N-oxides with arynes afforded 2-(2-hydroxyphenyl)quinolines and 7-membered pentacyclic oxazepino[4,5-a]quinolines.