ABSTRACT In the asymmetric Michael addition catalyzed by Jacobsen‐type cobalt–salen catalysts and their fluorous‐tagged derivatives, minimal modification of the salen ligand framework through the introduction of fluorous tags at the 3,3′‐positions significantly influenced both catalytic activity and enantioselectivity. While the salen backbone and chiral diamine source were kept unchanged, fluorous cobalt–salen complexes efficiently promoted the reaction, whereas nonfluorous analogues exhibited low or negligible stereoselectivity. Notably, under optimized conditions, the fluorous catalyst afforded the opposite enantiomer compared with a conventional nonfluorous Jacobsen‐type catalyst, demonstrating that minimal fluorous‐tag modification of the salen ligand framework can markedly alter the stereochemical outcome of the reaction.
Gotoh et al. (Wed,) studied this question.