In Situ Generation of Allenes and their Application to One-Pot Assembly of Functionalized Fluoreno[3,2-b]furans by Calcium-Catalyzed, Regioselective, 3-Component Reactions

Abstract

We have developed a novel synthetic methodology for the preparation of tetra-annulated fluorenofurans and fluorenopyrans using calcium(II)-catalyzed one-pot, three-component reaction. In this reaction, tert-propargyl alcohols react with 1,3-dicarbonyls to form tetra-substituted allenes, which are subsequently undergoing regiodivergent annulation with sec-propargyl alcohols to produce the fluorene-fused furan compounds. Broad substrate scope, regioselectivity, gram-scale synthesis, and benzylic functionalization of products are some of the highlights of this protocol.