Efficient Asymmetric Synthesis of 4H‐Chromene Derivatives through a Tandem Michael Addition–Cyclization Reaction Catalyzed by a Salen–Cobalt(II) Complex

Abstract

AbstractThe asymmetric synthesis of 2‐amino‐5‐oxo‐5,6,7,8‐tetrahydro‐4H‐chromene derivatives was achieved through a tandem Michael addition–cyclization reaction of easily available cyclohexane‐1,3‐dione and ethyl 2‐cyano‐3‐phenylacrylates. Moderate to good yields (up to 81 %) and high enantioselectivities (up to 89 % ee) were obtained with a chiral salen–cobalt(II) complex. This process was air tolerant and easily performed, which provides an efficient method for the synthesis of chiral 4H‐chromene derivatives.