Cyclic boronic hemiesters, boron isosteres of lactones, display unique and valuable chemical properties. Herein, we report a novel method for their synthesis via nickel-catalyzed decarbonylative borylation, enabled by electron-rich phosphine ligands to achieve a formal “C-to-B” atom swap. This strategy efficiently transforms a variety of coumarin derivatives and seven-membered dibenzolactones into the corresponding benzoxaborines, showcasing broad functional group tolerance and synthetic versatility.

Abstract

We report a carbon-to-boron “C-to-B” atom swap reaction to transform readily available coumarins into their isosteric benzoxaborins via a net replacement of the C═O group with a B─OH moiety. These conditions were applied to coumarin natural products and other 6–7-membered lactones (25 examples, 29%–93%). We leverage this methodology to transform a flat polyaromatic hydrocarbon into three-dimensional tribenzo[b.d.f]oxepines through a series of atom-swapping reactions followed by ring expansion via the oxaborin intermediate.