New cascade reactions starting from acetylenic ω-ketoesters: an easy access to electrophilic allenes and to 1,3-bridgehead ketones

Acetylenic ω-ketoesters bearing a three carboncarbon bond spacer reacted smoothly with tetra-n-butylammonium fluoride and with potassium tert-butoxide to afford either electrophilic allenes or 1,3-bridgehead ketones, the latter being potentially useful molecules for the synthesis of biologically active compounds like Garsubellin A and Hispidospermidin.