Ketone Synthesis from Benzyldiboronates and Esters: Leveraging ?-Boryl Carbanions for Carbon-Carbon Bond Formation.

ABSTRACT: An alkoxide-promoted method for the synthesis of ketones from readily available esters and benzyldiboronates is described. The synthetic method is compatible with a host of sterically differentiated alkyl groups, alkenes, acidic protons ? to carbonyl groups, tertiary amides, and aryl rings having common organic functional groups. With esters bearing ?-stereocenters, high enantiomeric excess was maintained during ketone formation, establishing minimal competing racemization by deprotonation. Monitoring the reaction between benzyldiboronate and LiO^tBu in THF at 23 °C allowed for the identification of products arising from deborylation to form an ?-boryl carbanion, deprotonation, and alkoxide addition to form an "-ate" complex. Addition of 4-trifluoromethylbenzoate to this mixture established the ?-boryl carbanion as the intermediate responsible for C-C bond formation and ultimately ketone synthesis. Elucidation of the role of this intermediate leveraged additional bond-forming chemistry and enabled the one-pot synthesis of ketones with ?-halogen atoms and quaternary centers with four-different carbon substituents.

SUBMITTER: Lee B 

PROVIDER: S-EPMC7047910 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature