Defluorinative Hydroxylation Promoted by Silica to Access Optically Pure Hexahydrofuranocarbazole via [4+2] Addition Reaction

Abstract

Crafting an efficient strategy for the synthesis of biologically active and functionally rich hexahydrofuranocarbazole is a highly desirable but demanding pursuit. This research elucidates a groundbreaking strategy involving an unanticipated defluorinative hydroxylation reaction facilitated by silica gel, yielding highly enantio‐ and diastereoselective hexahydrofuranocarbazole frameworks. This method results in the formation of five consecutive chiral centers, including three quaternary stereocenters and an all‐carbon spiro center, via an aminocatalytic asymmetric remote [4+2] addition process. The developed methodology allows for the construction of a diverse array of products (24 examples, up to >99 % ee and 17 : 1 dr), reflecting its notable substrate scope. Furthermore, we demonstrate the feasibility of gram‐scale synthesis and control experiments that underscore the methodological advancements and provide insights into the underlying mechanism.