N. Wu, L. J. Deng, L. Z. Liu, Q. Liu, C. C. Li*, Z. Yang*

Chem. Asian J. 2013, 8, 65

Which way? Palladium thiourea catalyzed Pauson–Khand reaction of norbornene with substituted alkynoates to afford selectively either α-carboxylated adducts or β-carboxylated adducts with the reverse regioselectivity has been demonstrated for the first time. Control of the regioselectivity in this transformation is governed by the addition of LiCl. A mechanistic interpretation to account for this observed regioselectivity is presented.