Nitrogenation of Alkynes with Nitrones to Prepare Functionalized [1,4]Oxazinones through Csp-Csp Bond Cleavage.

Herein, we report a novel strategy of hypervalent iodine(III) compound-mediated selective C-C bond cleavage of alkynes and C═N/N-O bond cleavage of nitrones and recombination of C-C/C-O/C-N multiple bonds to access various functionalized [1,4]oxazinones bearing a vicinal carbon stereocenter in good yields and high diastereoselectivity. Mechanistic studies revealed that the reaction undergoes a domino [4 + 3] cycloaddition, 1,3-rearrangement of N-O bond, intramolecular cyclization, dearomatization, and rearomatization over four steps in a single flask. The present method features good functional group tolerance, broad substrate scope, and C-C/C═N/N-O multiple bonds cleavage and recombination.

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

We described an iron(III) and BF·OEt-promoted oxygen transfer reaction of -aryl-α,β-unsaturated nitrones to prepare various ,-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 ,-difluoroboron β-ketoiminates, and iron(III) combined with BF·OEt played as cocatalyst to promote the oxygen transfer reaction through intramolecular cyclization and N-O bond cleavage. More importantly, an estrone-derived ,-difluoroboron β-ketoiminate was easily prepared in 40% yield from estrone in four steps.