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

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. [ABSTRACT FROM AUTHOR]