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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
Published on: February 6, 2019
Net Intermolecular Silyloxypyrone-Based (5+2) Cycloadditions Utilizing Amides as Enabling and Cleavable Tethers
Susanna N Angles1, Wentao Guo2, Kwabena Darko1
1Department of Chemistry, Illinois State University, Campus Box 4160, Normal, Illinois 61790-4160, United States.
None:
Silyloxypyrone-based (5+2) cycloadditions were facilitated by amides that allowed for increased reactivity and a pathway for cleaving the tether to afford net intermolecular cycloadducts. Various amides underwent facile cycloaddition, and several experiments revealed steric and electronic factors that accelerate the reaction. tert-Butyl amides reacted faster than less hindered variants in multiple cases. In the case of dearomative oxidopyrylium-indole (5+2) cycloadditions, an amine-based tether was ineffective, whereas amides enabled this powerful transformation. Theoretical calculations evidenced a concerted asynchronous reaction in which the amide facilitates a conformational driving force enabling cycloaddition. Finally, a one-pot acylation/(5+2) cycloaddition/nucleophilic lactam opening and other examples of tosyl lactam opening of a modified cycloadduct were demonstrated.
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