Photocatalytic Silyl Radical Cyclization: Highly Stereoselective Synthesis of Alkenyl/Silyl-Functionalized ( <i>E</i> )-γ-Lactams

The traditional radical tandem cyclization of 1,6-enynes with silyl radicals happens through silyl radicals first adding to the triple bond to get alkenylsilyl compounds. Herein we disclosed a different regioselective silyl radical cyclization with 1,6-enynes to access alkenyl and silyl difunctionalized (<i>E</i>)-γ-lactams. Notably, the previous radical synthesis methods for γ-lactams are mostly of (<i>Z</i>)-configuration. This method can readily provide a series of (<i>E</i>)-γ-lactam derivatives through the radical cascade cyclization of the <i>in situ</i> generated silyl radicals with 1,6-enynes. Furthermore, this metal-free strategy proceeds under mild reaction conditions, exhibits excellent regioselectivity and stereoselectivity and 100% atom economy, as well as enables the efficient construction of C_sp3-Si bonds.