Direct synthesis of fluorene-based spirolactones through a BF3-promoted spiroannulation of α-keto acids and o-alkynylbiaryls†
Abstract
A novel and practical approach to substituted fluorene-based spirolactones has been described via an efficient BF3-promoted spiroannulation of α-keto acids and o-alkynyl biaryls. This metal-free cascade reaction proceeds smoothly at room temperature, and provides a wide range of structurally diverse products in good to excellent yields under mild conditions.