Efficient synthesis of 3-hydroxy chromones via oxidative cyclization mediated by lipase

Vitreoscillahemoglobin: a natural carbene transfer catalyst for diastereo- and enantioselective synthesis of nitrile-substituted cyclopropanes

“…1–10 Over the past decades, the scope of enzymatic applications in non-natural reactions has significantly expanded, thereby broadening their utility in chemical synthesis. 11–31 Hemoproteins, including cytochrome, peroxidase, myoglobin, and hemoglobin, have demonstrated the ability to mediate carbene-type C–C bond formations such as cyclopropanation, C–H insertion and ylide formation. 32–39 These remarkable achievements have unveiled an entirely new and unexpected realm of organic chemistry.…”

Visible-Light-Induced Synthesis of 3-Alkyl Chromones under Catalyst- and Additive-Free Conditions

“…9 As an alternative to the metal photosensitizers and organic dyes, enzymes as biocatalysts also play an important role in the construction of diverse chromones. 10 In 2022, Zhu's group disclosed that 3-substituted chromone generation of enaminones with glycine esters through cooperative catalysis of photoredox and an enzyme, which is a practical and efficient strategy under mild conditions in one pot (Scheme 1c). 11 However, those methods generally require the use of catalysts and additives, which inevitably increase the cost and may limit their practical applications.…”

“…Recently, photochemical synthesis has experienced a resurgence in interest as a powerful synthetic tool because of its mild reaction condition, which meets the perspective of sustainable and green chemistry. , In 2020, Mkrtchyan and laroshenko provided two simple, concise, and facile routes for the straightforward assembly of 3-substituted chromones through visible-light-mediated arylation reactions of ortho -hydroxyaryl enaminones with two different reagents, namely, aryldiazonium tetrafluoroborates and diaryliodonium triflates, utilizing Eosin Y and Ru­(bpy) 3 Cl 2 ·6H 2 O as photocatalysts, respectively (Scheme b) . As an alternative to the metal photosensitizers and organic dyes, enzymes as biocatalysts also play an important role in the construction of diverse chromones . In 2022, Zhu’s group disclosed that 3-substituted chromone generation of enaminones with glycine esters through cooperative catalysis of photoredox and an enzyme, which is a practical and efficient strategy under mild conditions in one pot (Scheme c) .…”

Cascade in Situ Iodination, Chromone Annulation, and Cyanation for Site-Selective Synthesis of 2-Cyanochromones

“…Among the readily available main building blocks, the o -hydroxyphenyl enaminones have been identified as particularly excellent candidates in the synthesis of functionalized chromones by means of tandem alkenyl C–H elaboration and chromone annulation . Especially in the period of the past decade, the enaminone-based chromone synthesis has gained splendid success by offering practical accesses to chromones containing highly enriched carbon, halogen, chalcogen, amine, or oxygen substituents. However, due to the inherently higher activity of the α-carbon site in the enaminones structure, the resultant chromones correspondingly bear the newly introduced functional group in the C3-site (Scheme A).…”