Palladium-catalysed heteroannulation with acetylenic compounds: synthesis of benzofurans1

A Simple and Efficient Synthesis of 2,3-Diarylnaphthofurans Using Sequential Hydroarylation/Heck Oxyarylation

“…17 Since then transition metal catalyzed coupling/ cyclization of suitably functionalized alkynes as starting materials has been focus for the synthesis of 2,3-diarylbenzofurans and 2,3-diarylnaphthofurans. [18][19][20][21] A number of methods have been developed for synthesis of 2,3-diarylbenzofurans but synthetic routes for naphthofurans are limited, 11,14 and synthesis of diversified naphthofurans still presents major challenge in organic synthesis.…”

Palladium-Catalyzed Alkynylation of Aryl and Hetaryl Halides: A Journey from Conventional Palladium Complexes or Salts to Palladium/Carbon

“…This observation, also noted by others, 7 prompted us to examine the reactivity of iodoarene 3, possessing a nucleophilic substituent at the ortho position, towards terminal alkynes as represented in Scheme 1. Accordingly, the reaction of o-iodophenol or o-iodobenzoic acid with terminal alkynes provided 2-subsituted benzofurans 8,9 or 3-ylidene phthalides/3-substituted isocoumarins 10,11 under palladium-copper catalysis. Notably, a similar method was utilized earlier to prepare the furopyridine/benzofuran ring system.…”

Synthesis of aromatic heterocycles

“…Details have been published of the sequential palladium catalysed coupling of 2-iodophenols with alk-1-ynes and endo cyclisation to 2-substituted benzofurans. 23 With silyl protected alkynols the method provides a route to benzofuran-3-methanol (Scheme 8) and to other alkan-3-ols. 24 A variant which leads to 2,3-disubstituted benzofurans is to carry out the reaction with allyl 2-alkynylphenyl ethers; for example, the ether 17 gave 3-allyl-2-methylbenzofuran 18 (76%) on palladium(0) catalysed cyclisation.…”