SYNTHESIS OF ALPHA-DIKETONES BY DIRECT, LOW-TEMPERATURE, INSITU NUCLEOPHILIC ACYLATION OF ESTERS BY ACYLLITHIUM REAGENTS

Addition of n-, sec-, or tert-butyllithium to a CO-saturated solution of an ester, R'CO2R'' in a solvent system of 4:4:1 (by volume) THF/Et2O/pentane at -110-degrees-C (or at -135-degrees-C in 3:1 (by volume) Me2O/THF), followed by hydrolysis with saturated aqueous NH4Cl, results in the formation of alpha-diketones, BuC(O)C(O)R', yellow liquids, in good yield. Similar reactions with diethyl succinate gave in one instance both t-BuC(O)C(O)CH2CH2CO2Et and t-BuC(O)C(O)CH2CH2C(O)C(O)Bu-t. The monoacylation product of dimethyl oxalate, t-BuC(O)C(O)CO2Me, readily formed a crystalline hydrate, t-BuC(O)C(OH)2CO2Me.