A Stereoselective Synthetic Route to 1,6-Dioxaspiro[4.4]non-3-en-2-ones from Cyclopropyl Alkyl Ketones and α-Ketoesters

The SnCl4-mediated reactions of cyclopropyl alkyl ketones with α-ketoesters afford a novel method for the synthesis of 1,6-dioxaspiro[4.4]non-3-en-2-ones with high stereoselectivities in moderate to good yields. This process is a sequential reaction involving a nucleophilic ring-opening reaction of the cyclopropane by H2O, an aldol-type reaction, and a cyclic transesterification mediated by Lewis acid.