β-cyano ketones;heterogeneous catalysis;solvent-free conditions;sustainable chemistry;A simple protocol for the conjugate addition of cyanide group to α,β-unsaturated ketones has been developed. By exploiting solvent-free conditions, the use of Amberlist-F (Amb-F) as heterogeneous fluoride catalyst, and trimethylsilyl cyanide (TMSCN) as reactant, β-cyano ketones have been obtained in good to excellent yields (73–99%) and with a low E-factor value (9–22). By the same procedure a representative cyano oxazolidinone and a cyano ester have been also prepared. The direct recovery and reuse of Amb-F in the β-cyanation process has been approached but proved to be impossible. As an alternative, a two-step protocol based on two different catalysts has been defined. Polystyryl-diphenylphosphine (PS-TPP) has been used for promoting the kinetic 1,2-addition affording a cyanohydrin trimethylsilyl ether, and Amb-F to promote a cyanide group 1,2-1,4-shift to obtain the β-cyano ketone. In this manner the recycling of both catalysts is possible. Further optimization of the two-steps protocol led to to very low E-factor values (0.8–1.3).
Synthesis of β-Cyano ketones promoted by a Heterogeneous Fluoride catalyst