Remote C?H functionalization using radical translocating arylating groups

摘要

Site selective chemical functionalization at unactivated C(sp3)?H bonds is highly challenging and recent successful studies mostly focus on the use of transition metal catalysis in combination with directing groups. Radical chemistry offers a complementary approach with the Barton and the Hofmann-L?ffler-Freytag reactions being landmark contributions in the area of remote C?H functionalization at unactivated aliphatic sites. Herein we introduce the concept of radical translocation arylation at unactivated secondary and tertiary C(sp3)?H bonds in various alcohols. The straightforward two-step sequence comprises an ionic alcohol sulfonylation with especially designed ortho-iodoaryl sulfonyl chlorides followed by a radical cascade reaction including aryl radical generation, remote radical translocation, aryl migration, reduction, and SO2 extrusion to give the corresponding γ-arylated alcohols. Moderate to good yields are obtained, remote C?H arylation occurs with excellent regioselectivity and for secondary C(sp3)?H bonds good to excellent stereoselectivity is achieved.