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Annulations of Enantioenriched Allenylsilanes with in Situ Generated Iminium Ions: Stereoselective Synthesis of Diverse Heterocycles

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journal contribution
posted on 15.01.2009, 00:00 by Ryan A. Brawn, James S. Panek
Highly enantioenriched allenylsilanes participate in Lewis acid mediated annulations with in situ generated iminium ions derived from tert-butyl carbamate and methyl carbamate to selectively form functionalized 4,5-dihydropyrroles and 4,5-dihyrooxazines, respectively. The dihydropyrrole products were further elaborated in a stereocontrolled vinylsilane terminated cyclization with in situ generated oxonium ions, resulting in pyranopyrroles.