Efficient Synthesis of Functionalized 4 H -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 4 H -chromene derivatives. 4 H -Chromene is an important structural fragment of many pharmaceuticals, natural products, and functional materials. The 4 H -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.