Fries rearrangement of aryl formates: a mechanistic study by means of 1H, 2H, and 11B NMR spectroscopy and DFT calculations.
1H, 2H, and 11B NMR spectroscopy has been used to study the mechanism of the Fries rearrangement of aryl formates promoted by boron trichloride by monitoring both the substrate and the Lewis acid. DFT calculations were employed to investigate the energetics of several reaction paths and to calculate NMR chemical shifts of key intermediates and products. After the formation of a 1:1 substrate-Lewis acid adduct, the rearrangement proceeds in two steps, beginning with the cleavage of the ester bond and the release of formyl chloride in situ, which, in turn, acts as a formylating agent, introducing an aldehydic functionality into the aromatic ring. The high regioselectivity (only the ortho product is obtained) is also accounted for by the proposed intermolecular, Lewis acid-assisted mechanism.
Bagno
Alessandro
A
Dipartimento di Scienze Chimiche, Università di Padova, Via Marzolo, 1 35131 Padova, Italy.
Kantlehner
Willi
W
Kress
Ralf
R
Saielli
Giacomo
G
Stoyanov
Edmont
E