Highly Site-Selective Direct C–H Bond Functionalization of Phenols with α‑Aryl-α-diazoacetates and Diazooxindoles via Gold Catalysis

An unprecedented
direct C–H bond functionalization of unprotected
phenols with α-aryl α-diazoacetates and diazooxindoles
was developed. A tris­(2,4-di-tert-butyl­phenyl)
phosphite derived gold complex promoted the highly chemoselective
and site-selective C–H bond functionalization of phenols and N-acylanilines with gold-carbene generated from the decomposition
of diazo compounds, furnishing the corresponding products in moderate
to excellent yields at rt. The salient features of this reaction include
readily available starting materials, unprecedented C–H functionalization
rather than X–H insertion, good substrate scope, mild conditions,
high efficiency, and ease in further transformation. To the best of
our knowledge, this is the first example of C–H functionalization
of unprotected phenols with diazo compounds.