A bicyclic [2.2.2]octadiene framework in which the ethano bridge contains a carbonyl group, an alkynyl and a trimethylsiloxy or hydroxy group has been utilized to generate alkoxyalkynylketenes via a retro-Diels-Alder reaction under relatively mild conditions (138 °C). This is an outstanding result since the retro-Diels-Alder reaction of [2.2.2]bicyclic compounds proceeds quantitatively but at unusually high temperatures (>500°C). The ketenes generated undergo [2+2] cycloadditions to alkynes in

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... sequence of events that lead to the formation of five-or six-membered ring products. We show using quantum chemical calculations that formation of five-or six-membered rings in the overall process is a function of the substituents on the alkynes used to trap the ketenes.