PREPARATION AND REACTIVITY OF THE ADDUCTS OF KETENE ALKYLSILYL ACETALS WITH ETHYL PROPIOLATE IN THE PRESENCE OF TITANIUM TETRACHLORIDE

The reaction of ketene alkylsilyl acetals with ethyl propiolate in the presence of TiCl4 led to intermediates whose reactivity was studied with electrophiles such as H2O, D2O, NBS, NCS, and PhSeCl to form glutaconate derivatives. Except in the case of the dimethylketene trimethylsilyl acetal, for which the reaction was stereospecific, with other ketene acetals the selectivity was lower. Similar results were observed in the reaction of these titanium intermediates with aldehydes and ketones. The results were interpretated as the formation of vinylic titanium intermediates (more stabilized in the case of the dimethylketene acetal) in equilibrium with the titanium allenolates.