Reactions of 4‐oxoalkanoic acids. III. Synthesis of 5‐Methyl‐ and 5‐Methylenepyrrolidin‐2‐ones by reaction of α‐angelica lactone with methylamine

Abstract

Abstract A re‐examination of the reaction of α‐angelica lactone with methylamine in water confirmed that 5‐hydroxy‐1,5‐dimethylpyrrolidin‐2‐one ( 5 ) was formed almost quantitatively in a very fast reaction. Dehydration of this compound by vacuum distillation, however, unexpectedly afforded 1‐methyl‐5‐methylenepyrrolidin‐2‐one ( 6 ), a compound with an exocyclic double bond, but not the isomeric 1,5‐dimethyl‐4‐pyrrolin‐2‐one ( 7 ) with an endocyclic double bond, as earlier claimed in the literature. With an excess of methylamine in methanol α‐angelica lactone was transformed into 5‐methylamino‐1,5‐dimethylpyrrolidin‐2‐one ( 8 ). This re‐examination was made to get levulinic acid derivatives with potential suitability for new syntheses of 1,4‐dicarbonyl compounds.