Base-Catalyzed Sequential 1,4-Addition/Intramolecular Cyclization/Aromatization Reaction: Synthesis of Benzofuro[3,2-b]pyridines

Abstract

An efficient K 2 CO 3 -catalyzed 1,4-addition/intramolecular cyclization/aromatization reaction of aurone-derived 1azadienes with trisubstituted allenoates has been developed, giving a series of benzofuro [3,2-b]pyridines in moderate to excellent yields. The reaction proceeded efficiently under an air atmosphere without the use of transition metal catalysts. This protocol provides a concise approach to benzofuro[3,2-b]pyridines.

(3 + 3) Annulation of acetoxy allenoates with enolisable carbonyl substrates leading to fused pyrans

“…1,2 Allenoates, as a subclass of allenes, also possess huge synthetic potential and numerous Lewis base catalysed annulations of allenoates have been published in recent years. 3 A detachable acetoxy substituent on the allenoate makes the system synthetically more usable and has been the subject of a multitude of novel transformations/annulations. The discovery of Lu's (3 + 2) cycloaddition brought out an emerging area of research for the construction of various carbo- and heterocycles.…”

Highly Regio- and Diastereoselective Phosphine-Catalyzed [2 + 4] Annulation of Benzofuran-Derived Azadienes with Allyl Carbonates: Access to Spiro[benzofuran-cyclohexanes]

“…Recently, BDAs have proven to be versatile building blocks since the pioneering work reported by Zhao’s group . These BDAs preferably acted as C4 synthons for the facile synthesis of benzofuran-fused heterocycles via [4 + n ] ( n = 1–6) cycloadditions owing to their polarized conjugation system, preexisting s-cis conformation, and driving force of aromatization (Scheme a) . However, due to the competing [4 + n ] annulations and conjugate additions, and the difficulty of dearomatization, the utilization of BDAs as C2 synthons in cycloadditions to access spiro-benzofuran scaffolds has been reported in the literature .…”

Synthesis of Heterocyclic‐Fused Furans and Dihydrofurans via (4+1)‐Annulation with Ylide: Exploration of Unique Reactivity Behavior of α‐Carbonyl Sulfoxonium Ylide

“…[3] The ring-structural skeleton as the functional substrate is less explored. , [4,5] On the other hand, judicial exploring the structural-electronic property of a bioactive skeleton behaving as a potential multifunctional skeleton is always valuable. It can undergo a tandem reaction with multi-functional substrate providing access to new chemotypes that possess structural integrity of the parent bioactive scaffold.…”