Scheme 2. (A) The original Michael reaction, discovered by A. Michael, comprises the addition of a malonate to a stabilised acrylate ester. (B) The 1,4-addition of heteroatom-centred nucleophiles to Michael acceptors, which is of central importance to this work. (C) β′-Substituted Michael acceptors, which can undergo addition–substitution reactions, maintaining the active double bond moiety.