C-H Triflation of BINOL Derivatives Using DIH and TfOH

Org Lett. 2019 Aug 16;21(16):6466-6470. doi: 10.1021/acs.orglett.9b02358. Epub 2019 Aug 6.

Abstract

C-H trifluoromethanesulfonyloxylation (triflation) of 1,1'-bi-2-naphthol (BINOL) derivatives has been established under mild conditions using 1,3-diiodo-5,5-dimethylhydantoin (DIH) and trifluoromethanesulfonic acid (TfOH). Up to eight TfO groups can be introduced in a single operation. The resulting highly oxidized BINOL derivatives can be successfully converted to 8,8'-dihydroxy BINOL and bisnaphthoquinone compounds. Mechanistic studies suggested that C-H triflation occurs in the form of an aromatic substitution reaction via the in situ formation of a radical cation.