Rapid Construction of Tetralin, Chromane, and Indane Motifs via Cyclative C−H/C−H Coupling: Four-Step Total Synthesis of (±)-Russujaponol F

The development of practical C−H/C−H coupling reactions remains a challenging yet appealing synthetic venture because it circumvents the need to prefunctionalize both coupling partners for the generation of C−C bonds. Herein, we report a cyclative C(sp³)−H/C(sp²)−H coupling reaction of free aliphatic acids enabled by a cyclopentane-based mono-N-protected β-amino acid ligand. This reaction uses inexpensive sodium percarbonate (Na₂CO₃·1.5H₂O₂) as the sole oxidant, generating water as the only byproduct. A range of biologically important scaffolds, including tetralins, chromanes, and indanes, could be easily prepared by this protocol. Finally, the synthetic application of this methodology is demonstrated by the concise total synthesis of (±)-russujaponol F in a four-step sequence starting from readily available phenylacetic acid and pivalic acid through the sequential functionalizations of four C−H bonds.