Methods for the synthesis of α-methylene lactones

Abstract

Methods for the construction of α-methylene-γ- and δ-lactones are surveyed, including applications to the synthesis of natural products [e. g. dl-alantolactone, (+)-arbusculin B, dl-avenaciolide, (-)-frullanolidc, dl-protolichesterinic acid, α-methylenc-γ-butyrolactone (tulipalin A), and others]. 1. Routes to α-Methylenc-γ-bulyrolactone and α-Methylene-δ-valcrolactone 1.1. Reactions of Alkynyl Alcohols with Nickel Carbonyl 1.2. Reductive Animation of α-Formyl Lactones 1.3. Acid or Metal-Ion Promoted Cyclopropane Rearrangements 1.4. α-Methylene Insertion via Wittig Reaction 1.5. Reductive Elimination of α-Formyl Lactones 1.6. The Mannieh Route to α-Methylcne Lactones 2. Construction of the α-Methylene Unit from Preformed Lactone Rings via Their Fnolates 3. Miscellaneous Routes to α-Methylene Lactones 4. Protection of α-Methylene Lactones 5. Conclusions.