Vinylalumination for the Synthesis of Functionalized Allyl Alcohols, Vinylepoxides, and α-Alkylidene-β-hydroxy-γ-lactones

A modified hydroalumination protocol for the preparation of [α-(ethoxycarbonyl)vinyl]diisobutylaluminum and its β-methyl or -phenyl analogues was developed. These vinylaluminum reagents react with aldehydes and ketones to provide the corresponding functionalized allyl alcohols in good to excellent yields. Perfluoroalkyl and -aryl carbonyl compounds, α-keto esters, α-acyl cyanides, and α-acetylenic ketones provide the corresponding α-hydroxyalkenes in high yields. The allyl alcohol product ratios from the vinylalumination of unsymmetrical α-diketones with [α-(ethoxycarbonyl)-vinyl] diisobutylaluminum and its β-methyl or -phenyl analogues depend on the steric and electronic environments of the ketones as well as the reagents. The products from the vinylalumination of α-bromoaldehydes and -ketones were cyclized with K₂CO₃ or KF under nonaqueous conditions to provide functionalized vinylepoxides in high yields. Vinylaluminations of keto-protected pyruvaldehyde provided the products, which were converted to a-alkylidene-β-hydroxy-β-lactones.