Temperature-Dependent Diastereodivergent [4+3] Annulation: Synthesis of Ferrocene Fused Azepines via Rh(III)-Catalysis

Herein, we disclose the first temperature-dependent diastereodivergent [4+3] annulation of ferrocene-p-tosylamides via C-H activation with allenes by Rh-catalyst. At room temperature, Rh-catalyzed [4+3] annulation selectively offered one diastere-omer (>20:1 dr), whereas at 60 ᵒC, another diastereomer was obtained exclusively with >20:1 dr. The control experiments, isotopic labeling study, and DFT calculations suggested that the reaction proceeds via a σ-bonded rhodacycle avoiding steric repulsion between the phenyl ring of allene and Cp* of Rh-catalyst. Consequently, reductive elimination offered a kinetically con-trolled diastereomer at room temperature. Under heating (60 ᵒC) conditions, kinetically controlled diastereomer undergoes C-N bond ring opening to afford completely thermodynamically controlled diastereomer.