Lewis acid promoted additions of cyclopropanes to iminium salts: a new possibility for α-methylene-γ-butyrolactone synthesis

Abstract

Methyl 2-siloxycyclopropanecarboxylates (1) smoothly add to dimethylmethyleneammonium trifluoromethanesulphonate, generated in situ, or to the corresponding minium chloride (4) in the presence of TiCl₄, giving α-aminomethylated γ-oxoesters (6) in good yield; these can serve as precursors for α-methylene-γ-butyrolactones (7) as well as for acrylic ester derivatives (8).