C−H Bond Functionalization via Hydride Transfer: Direct Coupling of Unactivated Alkynes and sp³ C−H Bonds Catalyzed by Platinum Tetraiodide

We report a catalytic intramolecular coupling between terminal unactivated alkynes and sp(3) C-H bonds via through-space hydride transfer (HT-cyclization of alkynes). This method enables one-step preparation of complex heterocyclic compounds by alpha-alkenylation of readily available cyclic ethers and amines. We show that PtI(4) is an effective Lewis acid catalyst for the activation of terminal alkynes for hydride attack and subsequent C-C bond formation. In addition, we have shown that the activity of neutral platinum salts (PtX(n)) can be modulated by the halide ligands. This modulation in turn allows for fine-tuning of the platinum center reactivity to match the reactivity and stability of selected substrates and products.