A key area of amine synthesis research has been the development of new methodologies for N-alkylation to overcome issues intrinsic to common procedures such as reductive amination and the nucleophilic substitution of alkylating agents, including over-alkylation, poor atom economy, and unsustainable reagents. The most widely developed of these, borrowing hydrogen catalysis, has seen further application in the synthesis of saturated N-heterocycles through the N-alkylation of amines with terminal diols. These redox neutral annulation reactions allow for N-substituted heterocycles to be synthesised with water as the sole by-product, but typically require forcing conditions and are largely limited in scope to benzylamine and aniline derivatives.