Synthesis of Tricyclic β-Methylene Spiro Lactones Related to Bakkenolides by Successive Radical Cyclization−High Pressure Diels−Alder Reactions
作者:Thomas G. Back、Patricia L. Gladstone、Masood Parvez
DOI:10.1021/jo960111+
日期:1996.1.1
piperylene failed at ambient pressure, but proceeded in generally good yield in the presence of various Lewis acids at pressures of ca. 16 kbar, to give mixtures of beta-exo, alpha-endo, and beta-endo cycloadducts 19, 21, and 23, respectively. The preponderance of endo products 21 and 23, formed via highly hindered, but more compact, transition states was attributed to the high pressure and resulted in trans-dimethyl