Gold‐catalyzed Alkyne Hydroxylation: Synthesis of 2‐Substituted Benzo[b]furan Compounds

Abstract

A strategy concerning the synthesis of 2-substituted benzo[b]furan compounds from o-alkynyl phenols via a gold-catalyzed alkyne hydroxylation is described, which allows the rapid synthesis of various 2-substituted benzo [b]furan derivatives in excellent yields under mild conditions. The o-alkynyl phenol precursors were readily prepared with a Sonogashira coupling reaction.

Diverse reactivity of a tricoordinate organoboron L2PhB: (L = oxazol-2-ylidene) towards alkali metal, group 9 metal, and coinage metal precursors

“…Note that some of the results shown here were comparable to or even better than those with (Ph 3 P)AuCl as a precatalyst under similar conditions. 27 It is also noteworthy that these results demonstrated the first application of metal complexes featuring a neutral boron-based ligand in catalysis.…”

Ähnlichkeiten und Unterschiede innerhalb der “relativistischen” Triade Gold, Platin und Quecksilber in der Katalyse

“…102 Dies würde auch die höhere Menge an Katalysator (5 Mol‐%) erklären, die hier im Vergleich zur Umsetzung freier Phenole (0.5–5 Mol‐%) benötigt wird. Eine Au‐Katalyse103a erlaubt die Anwendung milderer Bedingungen bei ähnlich hohen Ausbeuten (Schema , Bedingung C, siehe auch Tabelle 2, Eintrag 22) 61…”

Synthesis of 2H-furo[2,3-c]pyrazole ring systems through silver(I) ion-mediated ring-closure reaction

“…Recently, 2-arylbenzo[ b ]furans were conveniently synthesized by the one-pot tandem Hiyama alkynylation/cyclization reaction between 2-iodophenol and (triethoxysilyl)alkynes [ 20 ]. In recent years silver and gold salts have found application as versatile and mild catalysts to access the benzo[ b ]furan ring system through intramolecular cyclization of 2-alkynylphenol substrates [ 21 ], including preparation of 2-benzofuranmethanamines [ 22 ] and 4-indolylbenzo[ b ]furans [ 23 ] in the presence of AgNO 3 and AgOTf, respectively, and 2-phenylbenzo[ b ]furans, where AuCl 3 or a mixture thereof with AgOTf has been used to promote the appropriate cyclization [ 24 ].…”