Photoredox-Catalyzed Hydrocarboxylation of Styrenes in Continuous Flow

Key words

photoredox catalysis - continuous flow - hydrocarboxylation - styrenes - phenylpropanoic acids - carbon dioxide

Significance

Jamison and co-workers present a photoredox-catalyzed hydrocarboxylation of styrenes using CO₂ and pentamethylpiperidine (PMP). The reactions are performed in flow (t _R = 8 min) to provide the anti-Markovnikov adducts in moderate to good yields with high degrees of chemo- and regioselectivity. Functional group tolerance and preliminary mechanistic investigations are disclosed.

Comment

This method offers a complementary approach to metal-catalyzed hydrocarboxylation reactions of styrenes, which often afford the corresponding Markovnikov adducts. Metal catalysis has recently been used to affect hydrocarboxylation reactions of simple olefins (M. Gaydou, T. Moragas, F. Juliá-Hernández, R. Martin J. Am. Chem. Soc. 2017, 139, 12161). A similar substrate expansion to simple alkyl olefins would bolster the synthetic capacity of this methodology.