PHOTOCATALYTIC PERFLUOROALKYL RADICAL ADDITION ONTO GLYCALS

A POSTIGO; MORA FLORES, ERWIN; MARIA LAURA UHRIG

RIO DE JANEIRO

Simposio; 30TH INTERNATIONAL CARBOHYDRATE SYMPOSIUM; 2022

SOCIEDAD BRASILEÑA DE INVESTIGACION EN CARBOHIDRATOS

Substitution of biological active compounds with fluoroalkyl RF moieties is a sought-after strategy to reach molecules with enhanced biological properties. Particularly, RF group-substitution conveys advantages over non-fluorinated analogs such as better bioavailability and augmented lipophilicity, caused by changes in drug pKa`s and the electron attracting properties of RF groups. Thus, we explored the photocatalyzed perfluoroalkyl radical additions onto glycals employing perfluoroalkyl iodides RF-I as sources of perfluoroalkyl radicals and the Ir[dF(CF3)PPy]2(dtbPy))PF6 photocatalyst in MeCN as solvent. Noteworthy, under irradiation with blue LEDs, two different products were obtained: on the one side, the expected 2-perfluoroalkyl-substituted glycals, which were also the major products when using Rose Bengal or Eosin Y as photocatalysts. This result was in accordance with those described previously by Ye and coworkers.1 Remarkably, 2-iodo-1-perfluoroalkyl-substituted glycosidic compounds were also obtained, as a result of a highly regioselective addition reaction of the RF moiety into C-1, followed by attachment of the iodine atom on C-2, both substituents in axial disposition. These unexpected results contrast with other radical additions onto 2-unsubstituted glycals. Additional experiments by performing the reaction in the presence of additives provided insight about the reaction mechanism.