A Concise Total Synthesis of Dictyodendrins F, H, and I Using Aryl Ynol Ethers as Key Building Blocks

We report a concise total synthesis of dictyodendrin F and the first total syntheses of dictyodendrins H and I in six steps. In these syntheses, aryl ynol ethers were employed as the key building blocks to introduce aryl and heteroaryl rings in the dictyodendrins. This rapid synthesis utilized a novel hetero-[2 + 2]-cycloaddition reaction between two aryl ynol ethers to yield a cydobutenone ring. The cydobutenone was sequentially converted into a highly substituted carbazole via a retro-4 pi/6 pi-electrocyclization-N-acylation cascade reaction to provide the dictyodendrin core. Consecutive intramolecular oxidative coupling and deprotection gave dictyodendrins F, H, and I.