The ketene tBu 2 C=C=O is prepared from tBu 2 C=O in three steps (performable as a two-stage operation) through elimination of HCl from the intermediate product tBu 2 CCl-CH=O. The acid tBu 2 CH-CO 2 H, obtainable in two, three, or four preparative stages from tBu 2 C=O, adds slowly to the ketene to produce the anhydride (tBu 2 CH-CO) 2 O. Elemental lithium together with ClSiMe 3 converts tBu 2 CCl-CH=O