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

Abstract

A facile cascade reaction for the site selective synthesis of 2-cyanochromones is described. By using simple ohydroxyphenyl enaminones and potassium ferrocyanide trihydrate (K 4 [Fe(CN) 6 ] 3 •3H 2 O) as starting materials and I 2 /AlCl 3 as promoters, the products are furnished via tandem chromone ring formation and C−H cyanation. The in situ formation of 3iodochromone and a formal 1,2-hydrogen atom transfer (HAT) process account for the unconventional site selectivity. In addition, the synthesis of 2-cyanoquinolin-4-one has been realized by employing corresponding 2-aminophenyl enaminone as substrate.

Visible Light Mediated Synthesis of 3‐Indolmethyl Chromones via the Cyclization of o‐Hydroxyaryl Enaminones with 3‐Indoleacetic Acids Catalyzed by Graphitic Carbon Nitride Adorned with Copper Nanoparticles

“…[14][15][16][17] The incorporation of the indolmethyl moiety is of immense interest in organic chemistry due to its prevalence in various pharmaceuticals and natural products. [18][19][20][21][22] One promising approach for introducing this portion involves decarboxylative transformations of carboxylic acids. [23,24] Chromones are equally important compounds found in nature and pharmaceuticals, that serve as key building blocks for the synthesis of heterocyclic molecules; [25,26] their functionalization through CÀ H bond activation being a valuable strategy.…”

“…The incorporation of the indolmethyl moiety is of immense interest in organic chemistry due to its prevalence in various pharmaceuticals and natural products [18–22] . One promising approach for introducing this portion involves decarboxylative transformations of carboxylic acids [23,24] .…”

Metal-free synthesis of difluoro/trifluoromethyl carbinol-containing chromones via tandem cyclization of o-hydroxyaryl enaminones

“…31 The tandem reaction involving chromone cyclization of o -hydroxyphenyl enaminones is a commonly used strategy for the synthesis of 3-substituted chromones. 32 For example, Yang and co-workers reported a highly efficient method for the synthesis of 3-CF 2 H/CF 3 -containing chromones by visible-light photoredox catalysis (Scheme 1b). 33 Wan's group developed a strategy for the synthesis of 3-trifluoromethyl chromones by o -hydroxyphenyl enaminone tandem cyclization reactions with CF 3 SO 2 Na as the trifluoromethyl source (Scheme 1c).…”

I2-DMSO mediated dual α,β-C(sp2)–H functionalization/bicyclization of o-hydroxyphenyl enaminones to construct C2,C3-disubstituted chromone derivatives: chromeno[2,3-b]pyrrol-4(1H)-ones

“…Only individual examples have been reported for their synthesis, affording C2-CN or N-heterocycle-substituted chromones exclusively. 5 To the best of our knowledge, dual α,β-C(sp 2 )–H functionalization of o -hydroxyphenyl enaminones to form C2,C3-disubstituted chromones has not hitherto been reported; achieving the subsequent cascade cyclization reaction between the two functional groups of C2,C3-disubstituted chromones will be a more challenging task. Based on our interest in enaminones, 6 herein, we disclose the first example of domino dual α,β-C(sp 2 )–H functionalization and dual cyclization of o -hydroxyphenyl enaminones to construct C2,C3-disubstituted chromones followed by formation of a new pyrrole ring via an intramolecular cascade cyclization between the two functional groups on C2,C3-disubstituted chromones (Scheme 1c).…”