A difluorocarbene-mediated cascade
cyclization reaction for rapid
access to gem-difluorinated 3-coumaranone derivatives
was developed. The difluorocarbene acts as a bipolar CF2 building block, which enables a homologation cyclization process
via sequentially reacting with the phenolate and the ester group on
the same substrate. The potential application of this synthetic approach
is demonstrated by a late-stage modification of diethylstilbestrol.
Mechanistic studies revealed the multiple crucial roles played by
the Ruppert–Prakash reagent.