alpha-Alkylidene-gamma-butyrolactones and delta-valerolactones via alkenylalumination: Biological intermediates and targets
α-Alkylidene-γ-butyrolactones and δ-valerolactones are very important as a class of compounds, occurring in a vast number of natural products, and showing a variety of biological activity. Alkenylalumination offers a direct route to the synthesis of butenolides and pyranones, as well as α-alkylidene γ-butyrolactones and δ-valerolactones. Our study is mainly focused on the synthesis of these biologically active lactones in a short and efficient manner. Chapter 1 introduces the importance of these lactones and reviews most of the early syntheses. Chapter 2 discussed the preparation of γ-aryl-α-alkylidene-γ-butyrolactones via the opening of aryl epoxides with alkenylaluminum reagents. Chapter 3 discusses the attempted preparation of γ-alkyl-α-alkylidene-γ-butyrolactones, including γ-trifluoromethyl-α-alkylidene-γ-butyrolactones. Chapter 4 discusses the preparation of tailored alkenylaluminum reagents for the synthesis of butenolides and pyranones. These have been converted to α-alkylidene-γ-butyrolactones and δ-valerlactones. Chapter 5 discusses the preparation of α-alkylidene-δ-valerolactones, including bicyclic lactones via the conjugate addition of ketone enolates to allylic acetates derived from alkenylalumination. Chapter 6 introduces a novel ring closing metathesis strategy for the synthesis of α-alkylidene lactones of varying ring size. This provides the future direction of this project. ^
P. V. Ramachandran, Purdue University.