FeCl3 Catalyzed Three‐Component Synthesis of Spirochromans and Dihydrocoumarins

Abstract An efficient approach towards the synthesis of substituted spirochromans and dihydrocoumarins from a three‐component reaction involving aromatic aldehydes, phenols and phenylene dithiolanes is described. This FeCl 3 catalyzed reaction utilizes either aromatic aldehydes or their acetals for condensation with phenols to generate o ‐quinone methides in situ which further undergo a formal [4+2] cyclization with phenylene dithiolanes. Careful control of temperature allows direct access to dihydrocoumarins by the removal of the thioacetal moiety.