Palladium-catalyzed intermolecular coupling of 2-haloallylic acetates with simple phenols, and sequential formation of benzofuran derivatives through the intramolecular cyclization

Recent Development in Palladium-Catalyzed Domino Reactions: Access to Materials and Biologically Important Carbo- and Heterocycles

“…The 2-fluoroallylic acetates provided the corresponding adducts in higher yields than 2-chloro and 2-bromoallylic in the most cases (Scheme ). The 3-alkyl-substituted 2-fluoroallylic acetates also allowed the reaction but with lower yields …”

“…The 3-alkylsubstituted 2-fluoroallylic acetates also allowed the reaction but with lower yields. 166 Elofsson et al improved the methodology employed by Tsay and co-workers 167 to prepare 7-methoxy-2-(phenyl)benzofuran-4-carboxaldehydes. They performed the Sonogashira coupling-cyclization between different aromatic alkynes and 2-bromo-or 2-iodo-3-hydroxybenzaldehydes using a lower catalyst loading of PdCl(C 3 H 5 )dppb (1 mol %) under microwave irradiation to obtain the corresponding 4-formyl-2-arylbenzofurans in moderate to good yields.…”

Synthesis of benzofurans from the cyclodehydration of α-phenoxy ketones mediated by Eaton’s reagent

“…7–9 Among them, transition-metal-catalyzed cyclization is most popular (Scheme 1, Path 1). 10–20 Many of these strategies rely on the cyclo-aromatization of alkynes or alkenes with phenol derivatives via inter- or intramolecular furan annulation catalyzed by Pd, Rh, Ag, Au, Co, Cu, and so on. In these pathways, expensive transition-metal catalysts are a prerequisite and the substrates are often synthesized via multi-step sequences.…”