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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
Published on: February 6, 2019
Lewis Acid-Promoted Enantioselective Dearomative Spirocyclizations of Allenes
Sergei Tcyrulnikov1, John M Curto1, Philip H Gilmartin1
1Department of Chemistry , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States.
Abstract:
A chiral oxazaborolidine combined with SnCl4 has been found to promote the dearomative spirocyclization of electron-rich benzyl allenyl ketones. The reaction outcome is sensitive to the nature of activating acid, which was rationalized using hard-soft acid-base (HSAB) theory. The spirocyclic product was obtained with up to 72% ee, which is the best result reported to date for these substrates. The formation of cross-conjugated or conjugated products is readily controlled by changing the oxygen-protecting groups.
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