Synthesis and Reactivity of Optically Active Spiroketals by Ring-Expansion of Chromium Carbene Complex-Derived Cyclobutanones.
Photolysis of cyclic chromium alkoxycarbene complexes with an optically active ene-carbamate gave spirofused, optically active cyclobutanones. Baeyer-Villiger ring expansion followed by further functionalization gave optically active spiroketals. Photochemical ring expansion of these spirofused cyclobutanones in the presence of acetic acid or thiophenol gave 2-acetoxy- or 2-(thiophenoxy)-4-spirofused tetrahydrofurans. Elimination of the thiophenoxy group gave a 3,4-dihydrofuran that underwent Heck arylation and photochemical cycloaddition with chromium carbene complexes to give cyclobutanones.
Bueno
Ana B.
AB
Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523.
Hegedus
Louis S.
LS