Radical 1,3-Difunctionalization of Allylboronic Esters with Concomitant 1,2-Boron Shift

Abstract

Summary Radical 1,3-trifluoromethylation/alkynylation of various allylboronic esters with concomitant 1,2-boron shift with alkynyl triflones is reported. These chain reactions proceed via CF3-radical addition to the allylic double bond, and the adduct radical undergoes 1,2-boron migration to give a translocated C-radical that is trapped by the alkynyl triflone. As products, 1,2,3-trisubstituted alkanes with the trifluoromethyl group at position 1 and the alkynyl functionality at position 3 are formed. The valuable boron moiety is retained in the product and is rearranged to position 2. By using trifluoromethanesulfonyl azide as the radical trapping reagent, the cascade provides a 1-trifluoromethyl-3-azidyl-alk-2-ylboronic ester as the product and Michael acceptors as trapping reagents in combination with the Langlois reagent as the CF3-radical precursor applying photoredox catalysis afford the corresponding 3-alkylated congeners in a three-component process. Further, the stereochemical course of the 1,2-boron migration and the trapping reaction are investigated.