Synthesis of the C(7)–C(22) Sector of (+)-Acutiphycin via O‑Directed Double Free Radical Alkyne Hydrostannation with Ph₃SnH/Et₃B, Double I–Sn Exchange, and Double Stille Coupling

Abstract

Herein a new double O-directed free radical hydrostannation reaction is reported on the structurally complex dialkyldiyne <b>11</b>. Through our use of a conformation-restraining acetal to help prevent stereocenter-compromising 1,5-H-atom abstraction reactions by vinyl radical intermediates, the two vinyl­stannanes of <b>10</b> were concurrently constructed with high stereocontrol using Ph₃SnH/Et₃B/O₂. Distannane <b>10</b> was thereafter elaborated into the bis-vinyl iodide <b>9</b> via O-silylation and double I–Sn exchange; double Stille coupling of <b>9</b>, O-desilylation, and oxidation thereafter furnished <b>8</b>