5-endo cyclizations of NHC-boraallyl radicals bearing ester substituents: characterization of derived 1,2-oxaborole radicals and boralactones

Wen Dai, Timothy R. McFadden, Dennis P. Curran*, Herbert A. Früchtl, John C. Walton*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)
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Abstract

EPR studies of radical hydrogen abstraction reactions of N-heterocyclic carbene (NHC) complexes of alkenylboranes bearing two ester substituents revealed not the expected boraallyl radicals but instead isomeric 1,2-oaxborole radicals. Such radicals are new, and DFT calculations show that they arise from the initially formed boraallyl radicals by a rapid, exothermic 5-endo cyclization. These spectroscopic and computational discoveries prompted a series of preparative experiments that provided access to a novel family of robust NHC-boralactones. A one-pot procedure was developed to access the boralactones directly from an NHC-borane (NHC-BH3) and dimethyl acetylenedicarboxylate.

Original languageEnglish
Pages (from-to)15868-15875
Number of pages8
JournalJournal of the American Chemical Society
Volume140
Issue number46
Early online date29 Oct 2018
DOIs
Publication statusPublished - 21 Nov 2018

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