FeCl3-catalyzed synthesis of functionally diverse dibenzo[b,f]oxepines and benzo[b]oxepines via alkyne-aldehyde metathesis

An efficient synthesis of dibenzo[b,f]oxepines and benzo[b]oxepines via FeCl3-catalyzed alkyne-aldehyde metathesis reaction is described. Structurally diverse dibenzo[b,f]oxepines and benzo[b]oxepines have been achieved in good yields with high regio- and chemoselectivity under mild conditions. Notably, among the various catalysts such as Fe(III), Au(III), In(III), Zn(II), Ag(I) and triflic acid, the alkyne-aldehyde metathesis reaction of 2-(2'-phenylethynyl-phenyloxy)-benzaldehyde is only catalyzed by environmentally friendly and sustainable iron(III) chloride.