Transient and Recyclable Halogenation Coupling (TRHC) for Isoflavonoid Synthesis with Site‐Selective Arylation

Abstract

A transient and recyclable C−H iodination has been designed for the synthesis of isoflavonoids through the domino reactions of o‐hydroxyphenyl enaminones and aryl boronic acids in the presence of catalytic KI and Pd catalyst. Instead of the conventional cross‐coupling strategy employing pre‐halogenated substrates, this method transforms raw C−H bond by means of a transient C−H halogenation to smoothly relay the subsequent C‐arylation. Consequently, such a method avoids the pre‐functionalization for C−halogen bond installation as well as the generation of stoichiometric halogen‐containing waste following the cross‐coupled product, disclosing an intriguing new coupling protocol to forge the C−C bond in the virgin area between classical C−X (X=halogen) bond cross coupling and the C−H activation.

Recent advances in transition metal-free annulation toward heterocycle diversity based on the C–N bond cleavage of enaminone platform

“…In the past decade, a range of 3-hydrocarbon functionalized chromones, including 3-alkylated chromones, 22 3-fluoroalkylated chromones, 23 3-arylated chromones, 24 3-vinylated chromones, 25 3-alkynylated chromones 26 and 3-acylated chromones, 27 had been synthesized via carbon functionalization, subsequent chromone annulation and final deamination under different reaction conditions and these developments had been reviewed by Wan et al 1 b in 2019 and Yu et al 1 d in 2021, respectively. Accordingly, only updated works in the chromone synthesis via such cascade reactions are introduced in this review.…”

Diversity‐Oriented Synthesis of Flavones and Isoflavones via Palladium/Norbornene Cooperative Catalysis

“…A number of methods for the assembly of flavones and isoflavones have already been developed, which can be roughly divided into two categories. [ 5‐11 ] One is through Claisen condensation, [ 12 ] Baker‐Venkataraman reaction [ 13 ] or Vilsmeier‐Haack reaction [ 14 ] of aromatic compounds, but most of these transformations only construct C2 and C3 monosubstituted chromones. The other is direct derivatization of chromone skeletons.…”

Stille coupling for the synthesis of isoflavones by a reusable palladium catalyst in water

“…Rh(I)-catalyzed oxidative-coupling of salicylaldehyde with phenylacetylene [34] and Cu(I)catalyzed cyclization of 3-(2-bromophenyl)-3-oxopropanals [35] gave isoflavones. Transition-metalcatalyzed C C bond cross-coupling, such as Negishi coupling by Pd [36] or Ni [37,38] and Suzuki-Miyaura reactions, [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] were widely applied for the synthesis of isoflavones in recent years. In addition, triarylbismuths were also employed as a coupling partner of 3-iodo or 3-trifloxychromones for Pd-catalyzed cross-coupling.…”