This review summarizes the recent advances (2016–2023) in the stereoselective metal-catalyzed hydrogenation of cyclic α,β-unsaturated ketones, lactams and lactones since considerable developments were made. Where possible the application of these methodologies in synthesis is outlined.

A N-heterocyclic carbene-phosphine iridium complex is presented for the efficient and selective mono-N-alkylation of sulfonamides with alcohols based on a borrowing hydrogenation strategy. Herein, water is the only by-product and this methodology thus offers a more environmentally benign and interesting alternative to the use of traditional alkylating reagents. This facile protocol tolerates a large number of (hetero) aromatic and aliphatic sulfonamides as well as (hetero) aromatic and aliphatic alcohols to obtain the desired product is high isolated yield (up to 98%). The alkylation completely retards after the formation of the secondary sulfonamide and no over-alkylation was observed in all cases. The option to run the reaction under solvent-free conditions as well as the scalability of this borrowing hydrogenation are key features of this protocol.

The activation of ethanol and methanol by VO2(+) in gas phase has been theoretically investigated by using density functional theory (DFT). For the VO2(+)/ethanol system, the activation energy (ΔE) is found to follow the order of ΔE(C(β)-H) < ΔE(C(α)-H) ≈ ΔE(O-H). Loss of methyl and glycol occurs respectively via O-H and C(β)-H activation, while acetaldehyde elimination proceeds through two comparable O-H and C(α)-H activations yielding both VO(H2O)(+) and V(OH)2(+). Loss of water not only gives rise to VO(CH3CHO)(+) via both O-H and C(α)-H activation but also forms VO2(C2H4)(+) via C(β)-H activation. The major product of ethylene is formed via both O-H and C(β)-H activation for yielding VO(OH)2(+) and VO2(H2O)(+). In the methanol reaction, both initial O-H and C(α)-H activation accounts for formaldehyde and water elimination, but the former pathway is preferred.