Borylative Radical Cyclizations of Benzo[3,4]cyclodec-3-ene-1,5-diynes and N-Heterocyclic Carbene-Boranes

Takashi Watanabe; Daisuke Hirose; Dennis P Curran; Tsuyoshi Taniguchi

doi:10.1002/chem.201700689

Borylative Radical Cyclizations of Benzo[3,4]cyclodec-3-ene-1,5-diynes and N-Heterocyclic Carbene-Boranes

Chemistry. 2017 Apr 24;23(23):5404-5409. doi: 10.1002/chem.201700689. Epub 2017 Mar 27.

Authors

Takashi Watanabe¹, Daisuke Hirose², Dennis P Curran³, Tsuyoshi Taniguchi¹

Affiliations

¹ School of Pharmaceutical Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan.
² Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan.
³ Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA.

PMID: 28205265
DOI: 10.1002/chem.201700689

Abstract

Borylative radical cyclization of benzo[3,4]cyclodec-3-ene-1,5-diynes to provide 5-borylated 6,7,8,9-tetrahydrobenzo[a]azulenes has been developed. The experimental results suggest that the reaction proceeds by a radical chain mechanism, in which di-tert-butyl hyponitrite (TBHN) works as a good radical initiator to form boryl radicals from N-heterocyclic carbene-boranes (NHC-boranes). The present reaction is a rare model that illustrates addition of boryl radicals to alkynes.

Keywords: alkynes; boron; main group chemistry; radical reactions; strained molecules.