The Diels-Alder reaction revolutionized organic chemistry by giving synthetic chemists the ability to controllably install organic frameworks, most notably via the [4 + 2] cycloaddition between a diene and a dienophile. Boroles (1) are five-membered, 4-π electron rings containing a highly activated diene due to their anti-aromatic state, and are promising candidates for Diels-Alder reactivity. The seminal example was reported by Eisch in 1969 and involves the reaction between pentaphenylborole and diphenylacetylene to furnish the bora-norboradiene (3). If small substituents are on boroles, dimerization occurs via a Diels-Alder mechanism akin to the cyclopentadienyl dimerization. In this work, the reactivity of boroles with substrates capable of acting as dienes and dienophiles is found to be much more diverse than the initial report almost 50 years ago.

Exploring Diels-Alder chemistry of boroles

255th National Meeting (2018)

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