Efficient Synthesis of Functionalized 4H-Chromenes via an Fe(OTf)3-Catalyzed Cyclization Reaction of Phenols and Ketones

The iron(III) triflate catalyzed cyclization reaction of phenols and ketones is described; the reaction provides a direct approach to 4H-chromene derivatives. 4H-Chromene is an important structural fragment of many pharmaceuticals, natural products, and functional materials. The 4H-chromene synthetic protocol possesses many advantages, such as using readily available and inexpensive starting materials and a non-toxic catalyst, high selectivity, and operational simplicity, which offer attractive industrial prospects from the point of view of green and sustainable chemistry.