Non-bonding 1,5-S•••O interactions govern chemo- and enantioselectivity in isothiourea-catalyzed annulations of benzazoles

Emily R. T. Robinson, Daniel M. Walden, Charlene Fallan, Mark D. Greenhalgh, Paul Ha-Yeon Cheong, Andrew D. Smith

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78 Citations (Scopus)
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Abstract

Isothiourea-catalyzed annulations between 2-acyl benzazoles and α,β-unsaturated acyl ammonium intermediates are selectively tuned to form either lactam or lactone heterocycles in good yields (up to 95%) and high ee (up to 99%) using benzothiazole or benzoxazole derivatives, respectively. Computation gives insight into the significant role of two 1,5-S•••O interactions in controlling the structural preorganization and chemoselectivity observed within the lactam synthesis with benzothiazoles as nucleophiles. When using benzazoles the absence of a second stabilizing non-bonding 1,5-S•••O interaction leads to a dominant CH•••O interaction in determining structural preorganization and lactone formation.
Original languageEnglish
Pages (from-to)6919-6927
Number of pages9
JournalChemical Science
Volume7
Issue number12
Early online date4 Jul 2016
DOIs
Publication statusPublished - 1 Dec 2016

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