Borylated Cyclopentanes via Atom Transfer Radical [3+2] Annulation

20 October 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Abstract. An atom transfer radical [3+2] annulation (ATRAn) reaction involving alkenyl boronic esters and homoallylic iodides provides a rapid access to polysubstituted borylated cyclopentanes. A variety of α-substituted vinylboronic esters are suitable substrates and offer unique opportunities for further modification of the formed 5-membered ring. For instance, the oxidation of the boronic ester to an alcohol allows to prepare products that corresponds to an annulation involving the enol form of acetone. Substitution of the iodide by a nucleophile such as lithium methoxide without modifying the boronic ester moiety is also feasible. Finally, by using a (3-acetoxyprop-1-en-2-yl)boronic ester, a facile 1,2-elimination reaction provided a methylenecyclopentane. In this case, the alkenylboronate radical trap acts as an equivalent to allene, a building block so far elusive for preparative radical reactions.


radical reaction
iodine atom transfer
α-boryl radical
vinylboronic esters

Supplementary materials

Experimental part
Full description of the experimental work, product characterization and copies of 1H and 13C NMR spectra.


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