Photocatalytic Silyl Radical Cyclization: Highly Stereoselective Synthesis of Alkenyl/Silyl-Functionalized ( E )-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 (E)-γ-lactams. Notably, the previous radical synthesis methods for γ-lactams are mostly of (Z)-configuration. This method can readily provide a series of (E)-γ-lactam derivatives through the radical cascade cyclization of the in situ 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 Csp3-Si bonds.