We present a diastereodivergent strategy for constructing bicyclic γ-lactones bearing quaternary carbon centers via ketone hydroacylation. By applying a Rh catalyst and JoSPOphos ligand, either the anti or syn bicyclic γ-lactones can be accessed with high enantio- and diastereoselectivities, depending on the choice of solvent, temperature, and counterion.
Rh-hydride catalysis solves a synthetic challenge by affording the enantioselective reduction of allenes, thereby yielding access to motifs commonly used in medicinal chemistry. A designer Josiphos ligand promotes the generation of chiral benzylic isomers, when combined with a Hantzsch ester as the reductant. This semireduction proceeds chemoselectively in the presence of other functional groups, which are typically reduced using conventional hydrogenations. Isotopic labelling studies support a mechanism where the hydride is delivered to the branched position of a Rh-allyl intermediate.
We report a Rh-catalyzed enantioselective cycloisomerization of α,ω-heptadienes to afford cyclohexenes bearing quaternary carbon centers. Rhodium(I) and a new SDP ligand promote chemoselective formation of a cyclohex-3-enecarbaldehyde motif that is inaccessible by the Diels–Alder cycloaddition. Various α,α-bisallylaldehydes rearrange to generate six-membered rings by a mechanism triggered by aldehyde C–H bond activation. Mechanistic studies suggest a pathway involving regioselective carbometallation and endocyclic β-hydride elimination.
Herein, we describe a regioselective Rh-catalyzed decarboxylative cross-coupling of β–keto acids and alkynes to access branched γ,δ–unsaturated ketones. Rh-hydride catalysis enables the isomerization of an alkyne to generate a metal-allyl species that can undergo carbon-carbon bond formation. Ketones are generated under mild conditions, without the need for base or activated electrophiles.
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