Divergent Synthesis of <i>α,β</i> -Unsaturated γ-Lactams via Tunable C–H Annulation of Acrylic Acids with Imines

We have developed a tunable C-H annulation strategy for the divergent synthesis of <i>α,β</i>-unsaturated γ-lactams from acrylic acids and imines. A ruthenium-catalyzed, redox-neutral vinylic C-H addition/cyclization with <i>in situ</i> generated formaldimines offers direct access to the fundamental lactam structure. Remarkably, higher temperatures divert the process through a tandem C-H cyclization-vinylogous aldol-dehydration sequence to yield methylene-γ-lactams. Moreover, employing rhodium catalysis broadens the scope to substituted imines, affording γ-substituted derivatives.