Carbanion Rearrangements. Collision-Induced Reactions of Enolate Negative Ions Derived From Dimethyl Succinates and Hexane-2,5-Dione

Enolate ion MeOCOCHCH2CO2Me fragments through the intermediacy of two ion complexes [ MeOCO (CH2=CHCO2Me)] and [ MeO-(O=C=CHCH2CO2Me)]. The major fragmentations produce CH2=C=C( OMe )O-+HCO2Me and O=C=CH- CH=C( OMe ). Similar ion complexes are formed from methyl-substituted succinates , but their fragmentations are often different from those outlined above: e.g. MeOCOC (Me)C(Me)2CO2Me - [ MeOCO (M2C=CmeCO2Me)] → CH2(Me)C=C(Me)CO2- Me+HCO2Me. The corresponding enolate from hexane-2,s-dione (MeCOCHCH2COMe) fragments through the acetyl anion complex [ MeCO (CH2=CHCO2Me)].