Synthesis of 4-substituted 3-(2-hydroxyphenyl)-quinolines through an unexpected iron(iii) chloride promoted reaction of cyclic imine dibenzo[b,f][1,4]oxazepines with alkynes†
An unexpected FeCl3-promoted reaction of cyclic imine dibenzo[b,f][1,4]oxazepines with alkynes was studied, leading to a series of 4-substituted 3-(2-hydroxyphenyl)-quinolines. A variety of substituted cyclic imines and terminal alkynes (arylacetylenes, conjugated enynes, and 1,3-diynes) were used for this reaction type resulting in the formation of the corresponding products in yields ranging from 34 to 88%. A reasonable reaction mechanism involving a tandem reaction procedure was proposed on the basis of control experiments. The reaction sequence demonstrated herein represents an efficient, yet practical method for the synthesis of novel 4-substituted 3-(2-hydroxyphenyl)-quinoline derivatives.