C–H Triflation of BINOL Derivatives Using DIH and TfOH

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