α-C–H Functionalization of π-Bonds Using Iron Complexes: Catalytic Hydroxyalkylation of Alkynes and Alkenes
Yiming Wang describes the iron-catalyzed hydroxyalkylation of alkynes and alkenes.
The α-functionalization of alkynes and alkenes with aldehydes reported in this study from the group of Professor Yiming Wang from the University of Pittsburgh (USA) is based on stoichiometric reactions of cationic alkene-iron π-complexes originally investigated by Myron Rosenblum and his research group in the 1970s. In particular, Rosenblum and co-workers observed that (i) cationic alkene complexes of cyclopentadienyliron dicarbonyl were strongly acidic, with α-protons undergoing quantitative deprotonation using triethylamine as the base; and (ii) the resulting δ-allyliron complexes were good nucleophiles. Subsequent studies revealed that these allyliron complexes are transition-metal analogues of allylstannanes, having similar nucleophilicity and reacting via an open-transition state SE2′ pathway. However, the propargylic functionalization of alkynes was not investigated in detail in these, nor in subsequent, studies.