Synthesis of cyclopenta[b]benzofurans via biomimetic oxidative phenol–enamine [3 + 2] cycloaddition

Abstract

A hemin/t-BuOOH-catalyzed oxidative phenol-enamine formal [3+2] cycloaddition has been developed, enabling environmentally benign synthesis of valuable cyclopenta[b]benzofuran scaffolds under sustainable reaction conditions with excellent atom- and step-economy. Mechanistic studies showed...

Visible Light‐Induced Synthesis of Fluorenes from α‐Biaryldiazoacetates

“…Our present approach to fluorenes is based on visible light‐induced photochemical reaction of diazo compounds that features mild reaction conditions (generated at ambient temperature in the absence of any transition metal catalysts), rendering it safer and more environmentally friendly compared to the traditional methods [52] (Scheme 1B). The current work was conducted as part of our ongoing research into green and sustainable orgainc transformations [53–56] . The UV‐vis absorption spectra of α ‐biaryldiazoacetates 1 a , 1 c , 1 f , and 1 u were determined with 0.006 mol/L concentration in MeCN solvent and all four compounds showed appreciable absorption in the visible region due to the extended conjugation within the structure of the compounds (Figure 2).…”

“…The current work was conducted as part of our ongoing research into green and sustainable orgainc transformations. [53][54][55][56] The UV-vis absorption spectra of αbiaryldiazoacetates 1 a, 1 c, 1 f, and 1 u were determined with 0.006 mol/L concentration in MeCN solvent and all four compounds showed appreciable absorption in the visible region due to the extended conjugation within the structure of the compounds (Figure 2). [57] We hypothesized that the diazoalkane, upon irradiation with low-energy visible light, would generate a carbene, which would undergo a catalyst-free intramolecular CÀ H bond insertion to form fluorene.…”

Development of novel transition metal-catalyzed synthetic approaches for the synthesis of a dihydrobenzofuran nucleus: a review

“…These parameters led the researchers to increase focus towards the iron-based catalysis for temperate and green reactions. 126 Bashir 127 et al in 2023 proposed a facile method for the synthesis of 2,3-dihydrobenzofurans 254 via [3 + 2] cycloaddition. In this regard, substituted hydroquinones 252 were made to react with N -arylated cyclic enamines 253 in the presence of a biomimetic catalyst, i.e.…”

Enantioselective Synthesis of 2,3,3a,8a-Tetrahydrofuro[2,3-b]benzofuran Scaffolds Enabled by Cu(II)/SPDO-Catalyzed [3+2] Cycloaddition of 2,3-Dihydrofuran and Quinone Esters

“…Oxidative [3+2] annulation , of phenol and olefin is the straightforward approach to accessing the dihydrobenzofuran moiety that could be conveniently transformed to a diverse range of natural products such as γ-rubromycin and callistrilones A–E. Notwithstanding, the elusive enantiocontrol and insufficient regioselectivity are still the major challenge.…”