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Stereoselective Synthesis of a Bicyclic Ketooxetane via a Thionium Ion-Mediated Cyclisation Reaction
31 December 2000 (online)
The synthesis of a bicyclic ketooxetane using as the key step the ethylaluminium dichloride-mediated cyclisation of a Z-silyl enol ether onto a thionium ion 'trigger' attached to a five-membered carbocyclic template is described. Attempted cyclisation of the analogous substrate possessing a six-membered ring did not afford the oxetane, but instead the product of 1,2-hydride shift. The mechanism of this unexpected transformation was conclusively established by analysis of the products of attempted cyclisation of a deuterium-labeled substrate.
ketooxetane - cyclisation - thionium - stereoselective - hydride shift