Surfactant-type protonic acid-promoted intramolecular cyclization of functionalized allylsilanes was studied in water for the synthesis of α-methylene-γ-lactone compounds. ω-Formyl-β-(acetoxymethyl)allylsilane afforded carbocyclic compounds in good yields, while the cyclization product was not obtained from the corresponding β-ethoxycarbonyl derivative. It was found that (Z)-β-(acetoxymethyl)allylsilane predominantly afforded the cis-product, while (E)-β-(acetoxymethyl)allylsilane afforded both cis- and trans-products at a ratio of almost 1 : 1. The stereoselectivity of the cyclization reaction was almost the same as a protonic acid-promoted reaction in CH2Cl2 and was explained by an interaction between the C(Si)-C(alkene) bond and the carbonyl moiety. The cyclization products were converted to α-methylene-γ-lactone compounds.
Keywords: allylsilane; aqueous organic reaction; stereochemistry; α-methylene-γ-lactone.