Combined Claisen Rearrangement and Oxidative Cyclization as a Route to Hydroxymethyl Dihydrofuran‐Annulated Coumarins

Abstract

A convenient and simple method for the synthesis of novel 3,4‐dihydrofuran‐annulated coumarins, 3‐(hydroxymethyl)‐2H‐furo[3,2‐c]chromen‐4(3H)‐ones 5a, 5b, 5c, 5d, 5e, 5f, 5g, by combined Claisen rearrangement and intramolecular regioselective oxidative cyclization of 4‐O‐allyl coumarin intermediates 3a, 3b, 3c, 3d, 3e, 3f, 3g using inexpensive oxidizing agent m‐CPBA is described. The reaction proceeds smoothly by tandem epoxidation/regioselective 5‐exo‐tet‐intramolecular ring opening. The structures of synthesized compounds are established on the basis of spectral data including IR, 1H NMR, and mass and elemental analyses.