Design, Synthesis, and Stereochemical Evaluation of a Novel Chiral Amine–Palladacycle

Efficient access to a designed phosphapalladacycle catalyst via enantioselective catalytic asymmetric hydrophosphination

A chiral phosphine auxiliary was generated with excellent ee via catalytic asymmetric hydrophosphination of 3-(naphthalen-1-ylmethylene)pentane-2,4-dione. The subsequent metal complexation of the monophosphine yielded two different coordination complexes depending on the reaction conditions. The ortho-palladation of both coordination complexes resulted in the formation of a single dimeric phosphapalladacycle complex that could be further converted to the monomeric bisacetonitrile derivative. Moreover, the palladium complex exhibits interesting oxophilicity as the stable bisaquo derivative could be isolated and characterized crystallographically. The catalytic potential of the phosphapalladacycle was also demonstrated.

Investigation of Functional Group Effects on Palladium Catalysed Asymmetric P–H Addition

The pincer catalysed asymmetric P–H addition of diphenylphosphine to 3-benzylidene-2,4-pentadione is herein reported. Albeit successful in catalysing a series of similar substrates, unexpected chelation of the dione substrate to a CP and CN palladacycle catalyst resulted in inactivation of the catalyst with adjacent coordination sites. Protected phosphine adducts were isolated and characterised, providing critical insights to the choice of catalyst for structurally distinct functional groups borne by the substrate.

σ-Alkenyl endo-palladacycle formation via regiospecific functionalisation of an unreactive NHC-tethered C(sp2)–H bond

A highly unusual cyclometallation reaction in which an aliphatic vinylic C(sp²)–H bond is activated to form a σ-vinyl palladacyclic–NHC complex is reported.