Here we report that palladium(0) complexes can coordinate in a η2 fashion to 1,3-dienes and significantly raise the energy of their highest occupied molecular orbital (HOMO) by donating the electrons from the d-orbitals to the empty antibonding molecular orbitals of double bonds (π*) via back-bonding. Thus, the uncoordinated double bond, as a more reactive partner on the basis of the principle of vinylogy, can directly attack imines, furnishing a formal hydrodienylation reaction enantioselectively. A chemoselective cascade vinylogous addition/allylic alkylation difunctionalization process between 1,3-dienes and imines with a nucleophilic group is also compatible, by trapping in situ formed π-allylpalladium species after initial ene addition. This π-Lewis base catalytic mode, featuring simple η2coordination, vinylogous activation, and compatibility with both conjugated neutral polyenes and electron-deficient polyenes, is elucidated by control experiments and density functional theory (DFT) calculations.

A chiral tertiary amine-catalyzed asymmetric γ-regioselective (4 + 3) annulation reaction of isatin-derived Morita− Baylis−Hillman carbonates and 1-azadienes was developed, delivering chiral azepane spirooxindoles with excellent stereoselectivity. In addition, by tuning the substituents of Morita−Baylis−Hillman carbonates, the switchable γ-(4 + 3) or α-(4 + 1) annulation reaction with o-quinone methides was observed to furnish benzo[b]oxepines or 2,3-dihydrobenzofurans, respectively, under similar catalytic conditions.

A readily available quaternary phosphonium salt containing a trifluoroacetonyl group and a tetrakis[3,5bis(trifluoromethyl)phenyl]borate (BAr F 4 − ) counterion was demonstrated to be a highly active Brønsted acid catalyst for Friedel−Crafts-type reactions of an array of electron-rich heteroarenes and aniline derivatives with isatin-derived ketimines, even at 0.1 mol % catalyst loadings.

The α-regioselective asymmetric [3 + 2] annulation reaction of Morita–Baylis–Hillman carbonates from isatins and activated ortho-vinylbenzaldehyses was developed by the catalysis of a chiral tertiary amine. The sequential N-heterocyclic carbene-mediated intramolecular Stetter reaction was conducted to finally furnish the bridged 5,8-methanobenzo[7]­annulen-9-one architectures incorporating a spirooxindole motif with excellent stereoselectivity.

Constructing fused hydrodibenzofuran architectures bearing a tetrasubstituted stereogenic center adjacent to an O atom is extremely difficult. Here we have developed an asymmetric dearomatizative Diels–Alder reaction using novel 2‐(3‐vinylbenzofuran‐2‐yl)ethan‐1‐one substrates and 3‐olefinic 7‐azaoxindoles. The reaction proceeds via in situ generation of a HOMO‐raised formal trienamine species with a chiral primary amine catalyst, producing highly complex tetrahydrodibenzo[b,d]furan derivatives with vicinal tetrasubstituted stereogenic centers in moderate yields with excellent stereoselectivity (dr>19:1, up to 98% ee).magnified image