Rounding things off: A cationic RhI/(R,R)‐walphos complex catalyzes an enantioselective [4+2] annulation of 2‐alkynylbenzaldehydes with cyclic electron‐deficient carbonyl compounds at room temperature (see scheme, R3=3,5‐(F3C)2C6H3, X=C or N). Enantioenriched spirocyclic benzopyranones and isatin derivatives are obtained in high yield (up to 97 %) and high enantioselectivity (up to >99 %).

Fantastic four: Tetrasubstituted alkenes have been prepared with high enantioselectivity by the title transformation. This reaction was successfully applied to the enantio‐ and diastereoselective synthesis of tetrasubstituted helical alkenes possessing both central and helical chirality (see scheme).

No abstract

Regio-, diastereo-, and enantioselective intermolecular [4 + 2] carbocyclizations of vinylarylaldehydes with alkenes and alkynes leading to substituted tetralones and 1-naphthols have been developed by using a cationic rhodium(I)/dppb or dppp complex as a catalyst.

Scheme 1. Rhodium-catalyzed enantioselective [4+2] annulation of 2alkynylbenzaldehydes 1 with carbonyl compounds 2.Scheme 2. Rhodium-catalyzed enantioselective synthesis of tetrasubstituted alkene 4 aa from 1 a and 2 a. cod = cycloocta-l,5-diene.