The reaction of ketene or dimethylketene with aldehydes or ketones in the presence of titanium or zirconium alkoxides gives essentially 8-hydroxyesters. By polyinsertion of ketene and aldehydes in the Ti-0 bond, di-, tri-, and tetraesters are formed. An excess of ketene produces acetyl derivatives of esters and 6-alkyl-3, 4, 5, 6-tetrahydro-2, 4-pyrandiones.
