HFIP Mediates a Direct C?C Coupling between Michael Acceptors and Eschenmoser's salt
A direct C?C coupling process that merges Michael acceptors and Eschenmoser's salt is presented. Although reminiscent of the Morita–Baylis–Hillman reaction, this process requires no Lewis base catalyst. The underlying mechanism was unveiled by a combination of kinetic, isotopic labelling experiments as well as computational investigations, which showcased the critical role of HFIP as a superior mediator for proton-transfer events as well as the decisive role of the halide counterion.