2-Pyrrolones 2-pyrrolidones

The importance of ring size holds also for tautomerism of -pyrrol-5-ones and. d -dihydro-6-pyridones. While the former compounds behave as cyclic 1-methyl-2-alkyl-2-hydroxy-5-pyrrolidones 179) (76) [or, on distillation, as the dehydrated l-methyl-2-alkyl-J -pyrrolones (77)], the latter compounds exist as acyclic N-methylamides of 8-oxo-acids (78) [as shown by infrared spectroscopy (/80)j. The dehydration of 78 during distillation to form l-methyl-2-alkyl-. -dihydro-6-pyridones (79) is achieved only with difficulty. 

A soln. of 5-(2-furyl)-2-pyrrolidone (obtained from furan and a mixture of 2-pyrrolone isomers) refluxed 10 min. under Ng in 2 N NaOH 4-amino-4-(2-furyl)butanoic acid. Y 95%. F. e. s. V. Bocchi and G. P. Gardini, Org. Prep. Procedures 1, 271 (1969). 

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