Reactions of ketenes. XX. Phenylketene dimethylacetal as synthon for the introduction of functionalized phenylethyl units

Phenylketene dimethylacetal (1) reacts with the α‐diazoketones to give the dihydrofurans 6. These compounds, as cyclic ortho esters, can undergo dealcoholation into the furans 2 and hydrolysis into the γ‐ketoesters 3 and into the γ‐ketoacids 4. Cyclopropane acetal 8, obtained starting from acetal 1 and ethyl diazoacetate, by heating leads quantitatively to functionalized ester 9. These synthetic methods enlarge the sphere of applicability of the electron‐rich alkene 1 as synthon in organic synthesis. Copyright © 1986 Journal of Heterocyclic Chemistr