Free radical reactions for heterocycle synthesis. Part 7: 2-Bromobenzoic acids as building blocks in the construction of spirobenzolactones and spirobenzolactams

A straightforward 2-step parallel synthesis for structurally diversified spiro compounds is developed. 2-Bromobenzoic acids are used as common building blocks to couple with a series of conjugated enoles or enamines. Sequential intramolecular free radical Michael additions lead to formation of spirobenzolactones, spirobenzolactams, spirobenzolactone-lactams, spiorbenzolactone-thiolactones, spiordilactones, and bridged-spirolactones.