Ultrasonic‐Assisted Hypervalent Iodine‐Catalyzed Cyclization of (E)‐2‐Hydroxystilbenes to Benzofurans Using Iodobenzene as Pre‐catalyst

Abstract

A rapid, and metal‐free approach for the synthesis of functionalized benzofurans 10 is illustrated by PhI 9 catalyzed cyclization of 2‐hydroxystilbenes 8. The 2‐hydroxystilbenes 8 were cyclized using 10 mol % PhI as a precatalyst, 2.0 equiv. of m‐CPBA as an oxidant and 2.4 equiv. of TFA as an additive at room temperature under ultrasonic irradiation condition. The functionalized benzofurans 10 were gained in good to excellent yields with shorter reaction times.

Ultrasound-assisted transition-metal-free catalysis: a sustainable route towards the synthesis of bioactive heterocycles

“…In 2020, Mangaonkar and co-workers demonstrated a highly convenient ultrasound-assisted strategy for the construction of functionalized benzofurans 11 via the cyclization of 2-hydroxystilbenes 10 ( Scheme 3 ). 58 Under the influence of 10 mol% of PhI as the pre-catalyst, m -CPBA as the oxidant, and TFA as additives, the products 11 were achieved in 63–87% yield at room temperature. In this reaction, the required iodine( iii ) species were produced in situ from the oxidation of PhI by m -CPBA and TFA.…”

Progress in organocatalysis with hypervalent iodine catalysts

“…The same cyclisations were developed by in situ generated active catalysts. 172 In 2020, Wang et al developed an oxidative fluorocyclisation of 1,1-disubstituted styrenes 268 with an internal oxygen nucleophile using in situ generated chiral iodine(III)-catalysts. The reaction employed C 2 -symmetric aryl iodides 269 as catalyst with HF-pyridine as fluorine source and mCPBA as oxidant.…”

Hypervalent iodine-mediated synthesis and late-stage functionalization of heterocycles

“…Very recently, the same group prepared 2-arylbenzofurans 224 by employing PhI 13 (10 mol %) as precatalyst in the presence of terminal oxidant m-CPBA and additive trifluoroacetic acid in CHCl3. 92 Scheme 59. Synthesis of 2-arylbenzofurans 224 using PIDA 6 as the catalyst.…”