Room-Temperature Metal-Catalyzed Hydrogen Borrowing Alkylation

Hydrogen borrowing describes a one-pot multistep sequence in which an alcohol is used as an alkylating agent. In comparison to a traditional alkylation reaction using alkyl halides, this is an attractive strategy: alcohol substrates are commercially abundant and stable, the process uses catalytic amounts of metal and base, and water is generated as the sole byproduct. Since seminal reports in the early 2000s, the field has been investigated extensively, but most hydrogen borrowing reactions operate under a high-temperature regime (76-200 °C), particularly those involving carbon-carbon bond formation. This review provides an overview of the current state of the art in room-temperature (≤30 °C) hydrogen borrowing reactions, including both carbon-carbon and carbon-nitrogen bond formation.