The carbonyl−olefin metathesis reaction could facilitate rapid functional group interconversion and allow construction of complicated organic structures. Herein, we demonstrate that elemental iodine, a very simple catalyst, can efficiently promote this chemical transformation under mild reaction conditions. Our mechanistic studies revealed intriguing aspects of the activation mode via molecular iodine and the iodonium ion that could change the previously established perception of catalyst and substrate design for the carbonyl−olefin metathesis reaction.

The non-benzenoid aromatic tropylium ion acts as an efficient promoter for carbonyl–olefin metathesis reactions.

Structural modification of the tetrahydroisoquinoline (THIQ) framework is of significant interest to organic chemists due to its central role in heterocyclic and medicinal chemistry. Here we demonstrate an efficient metal-free method for the oxidative functionalization of THIQs at the C1 position, which is amenable to a diverse range of C-C coupling reactions. These reactions proceed through a hydride abstraction involving the tropylium ion followed by quenching the generated iminium intermediates with nucleophiles to afford THIQ derivatives with excellent efficiencies and interesting selectivities.

The hydration of alkynes is one of the most atom‐economic and versatile synthetic protocols to access carbonyl compounds. This fundamental reaction, however, often requires transition‐metal catalysts or harsh reaction conditions to promote the addition of water to the carbon–carbon triple bond. In this work, it is demonstrated that the non‐benzenoid aromatic tropylium ion can be used as an organic Lewis acid promoter for the hydration of alkynes under simple reaction conditions with excellent outcomes.

The carbonyl–olefin metathesis reaction has become increasingly important in organic synthesis due to its versatility in functional group interconversion chemistry. Recent developments in the field have identified a number of transition-metal and organic Lewis acids as effective catalysts for this reaction. Herein, we report the use of simple organic compounds such as N-iodosuccinimide or iodine monochloride to catalyze the carbonyl–olefin metathesis process under mild reaction conditions. This work broadens the scope of this chemical transformation to include iodonium sources as simple and practical catalysts.