Inversion of the direction of stereoinduction in the coupling of chiral gamma,delta-unsaturated Fischer carbene complexes with o-ethynylbenzaldehyde.

[reaction: see text] A variety of gamma,delta-unsaturated carbene complexes that feature a stereogenic center at the beta-carbon couple with 2-ethynylbenzaldehyde to afford hydrophenanthrene derivatives with a high degree of stereoinduction. The direction of stereoinduction is opposite for examples where the stereogenic center is acyclic vs examples where it is within a ring.