Catalytic Enantioselective Synthesis of β-Allenyl Boronic Esters by Conjunctive Cross-Coupling with Propargylic Carbonates.

Enantioselective conjunctive cross-coupling with propargylic carbonates affords (β-boryl allenes as the reaction product. The reaction is found to proceed through the intermediacy of dimethoxyboronate complexes that are generated in situ by a strain-induced ligand exchange reaction.

Vinylidenation of Organoboronic Esters Enabled by a Pd-Catalyzed Metallate Shift.

Organoboron "ate" complexes undergo a net vinyl insertion reaction to give 1,1-disubstituted alkenyl boronic esters when treated with stoichiometric allyl acetate and a palladium catalyst. Reactions that employ vinyllithium afforded good to excellent yields after one hour, while reactions that employ vinylmagnesium chloride furnished modest to good yields after 18 hours.

Pd-Catalyzed Conjunctive Cross-Coupling between Grignard-Derived Boron "Ate" Complexes and C(sp) Halides or Triflates: NaOTf as a Grignard Activator and Halide Scavenger.

Catalytic enantioselective conjunctive cross-couplings that employ Grignard reagents are shown to furnish an array of nonracemic chiral organoboronic esters in an efficient and highly selective fashion. The utility of sodium triflate in facilitating this reaction is two-fold: it enables "ate" complex formation and overcomes catalytic inhibition by halide ions.

Gold-catalyzed dearomative spirocyclization of aryl alkynoate esters.

Aryl alkynoate esters undergo gold-catalyzed spirocyclization under mild conditions, affording spirolactones in high yields. This approach obviates the need for stoichiometric halogenating reagents typically employed for alkyne activation in related transformations. Water was found to play a critical role in governing the product selectivity.