Selective intermolecular oxidative cross-coupling of enolates, which is a bond-forming reaction between carbanion equivalents, remains as an unsolved issue despite its potential utility for the direct synthesis of unsymmetrical 1,4-diones. The main difficulty derives from the unavoidable homo-coupling. Our strategy depends on the selective one-electron oxidation of one enolate to afford an electrophilic carbonyl α-radical species, followed by trapping with another enolate. The present study demonstrates the selective oxovanadium(V)-induced cross-coupling between boron and silyl enolates.

Intermolecular oxidative cross-coupling of two different enolates is one of the most useful reactions to synthesize unsymmetrical 1,4-dicarbonyl compounds. In this study, the oxovanadium(V)-induced intermolecular oxidative cross-coupling of enolates afforded unsymmetrical 1,4-dicarbonyl compounds. Various boron and silyl enolates underwent the formation of ketone-ester, ester-ketone, ester-ester, amide-ketone and amide-ester coupling products . These results clearly show the versatility of the present oxidative cross-coupling protocol.

The oxovanadium(v)-catalyzed oxidative cross-coupling of enolates using O2 as a terminal oxidant is reported, where a boron enolate and a silyl enol ether were employed as enolates.

Combining everything: Oxovanadium(V)‐induced intermolecular oxidative cross‐coupling of enolates afforded unsymmetrical 1,4‐dicarbonyl compounds. Various boron and silyl enolates formed ketone–ester, ester–ketone, ester–ester, amide–ketone, and amide–ester coupling products. The V‐shaped figure written by using comets in the cover picture represents the vanadium reagent which is a key oxidant in this study. More information can be found in the Communication by Toru Amaya, Toshikazu Hirao et al. on page 1301 in Issue 12, 2017 (DOI: 10.1002/asia.201700470).

Selective oxovanadium(V)‐induced cross‐coupling between boron and silyl enolates yields unsymmetrical 1,4‐diketones.