Visible-light-driven spirocyclization of epoxides via dual titanocene and photoredox catalysis

Shuangjie Lin; Yuqing Chen; Fusheng Li; Caizhe Shi; Lei Shi

doi:10.1039/c9sc05601g

Visible-light-driven spirocyclization of epoxides via dual titanocene and photoredox catalysis

Chem Sci. 2019 Dec 9;11(3):839-844. doi: 10.1039/c9sc05601g.

Authors

Shuangjie Lin¹, Yuqing Chen¹, Fusheng Li¹, Caizhe Shi¹, Lei Shi¹

Affiliation

¹ Zhang Dayu School of Chemistry, State Key Laboratory of Fine Chemicals, Dalian University of Technology Dalian 116024 China [email protected].

Abstract

We describe the synergistic utilization of titanocene/photoredox dual catalysis driven by visible light for the radical opening/spirocyclization of easily accessible epoxyalkynes. This environmentally benign process uses the organic donor-acceptor fluorophore 2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN) as a photocatalyst and Hantzsch ester (HE) as an electron donor instead of stoichiometric metallic reductants. The photocatalytic conditions showed exceptionally high reactivity for the synthesis of privileged and synthetically challenging spirocycles featuring a spiro all-carbon quaternary stereocenter. Cyclic voltammetry (CV) studies suggest that Cp₂Ti^IIICl is the catalytically active species.