Iron(III) and BF 3 ·OEt 2 -Promoted O-Transfer Reaction of N -Aryl-α,β-Unsaturated Nitrones to Prepare Difluoroboron β-Ketoiminates.

We described an iron(III) and BF 3 ·OEt 2 -promoted oxygen transfer reaction of N -aryl-α,β-unsaturated nitrones to prepare various N , O -difluoroboron β-ketoiminates in good yields ranging from 24% to 87%. Control experiments revealed that the enaminone was the vital intermediate for the formation of N , O -difluoroboron β-ketoiminates, and iron(III) combined with BF 3 ·OEt 2 played as cocatalyst to promote the oxygen transfer reaction through intramolecular cyclization and N-O bond cleavage. More importantly, an estrone-derived N , O -difluoroboron β-ketoiminate was easily prepared in 40% yield from estrone in four steps.