Macrocyclic polyethers as enolate activators in homogeneous and heterogeneous systems

The ability of macrocyclic polyethers to activate enolates has been studied in the alkylation of deoxybenzoin (1) with butyl derivatives nBuY (Y = Br, I, OMes) catalyzed by crown ether PHDB18C6 (7) or cryptand [2.2.2,C-10] (8 ) under phase-transfer catalysis (PTC) and homogeneous (chlorobenzene) cond itions. The enolate reactivity is mainly determined by the ligand (cryptand > crown ether) and solvent (increasing with the polarity, in the order: to luene < chlorobenzene < 1,2dichlorobenzene). Regioselectivity of the reacti on is also remarkably affected by ligand and alkylating agent.