In Situ Generation of Allenes and their Application to One‐Pot Assembly of Functionalized Fluoreno[3,2‐<i>b</i>]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.