Catalytic Asymmetric Cationic Geranyl Cyclizations.

Cyclogeranyl motifs are important in natural products and terpene synthesis, yet their asymmetric formation from acyclic dienes remains challenging. Here, we report a general catalytic asymmetric cyclization of geranyl derivatives using confined chiral imidodiphosphorimidate (IDPi) Brønsted acids. In combination with fluorinated alcohol additives, the reaction proceeds under mild conditions with high efficiency and excellent regio- and enantioselectivity. The method accommodates diverse substrates, enabling access to fragrance-relevant scaffolds, retinal precursors, complex polycyclic terpenes, and even selective squalene cyclization. Mechanistic studies support a cooperative catalyst-additive hydrogen-bonding network and an asynchronous concerted, enzyme-like transition state within a confined chiral environment. This work provides a general solution for asymmetric geranyl cyclizations and expands the utility of confined Brønsted acid catalysis in biomimetic terpene synthesis.