Synthesis and Photochemistry of 5,5-Dimethyl-1H-pyrrol-2(5H)-one and Some N-Substituted Derivatives

Article abstract of DOI:10.1002/hlca.19920750435

In two steps 5,5-dimethyl-1H-pyrrol-2(5H)-one (3a) was prepared from 5,5-dimethylpyrrolidine-2,4-dione (=dimethyltetramic acid; 4) in 71percent overall yield (Scheme 1) and further converted to N-substituted derivatives 3b-f via acylation, alkylation, or methoxycarbonylation of its anion (Scheme 2).The substituents on the N-atom exert a strong influence on the photochemical reactivity (<2+2> photocycloaddition to 2,3-dimethylbut-2-ene, photocyclodimerisation, photoreduction) of these aza-enones 3 (Scheme 3).In general, N-alkyl compounds react much slower and with less efficiency than either the (N-unsubstituted) title compound 3a or its N-acetyl and N-(methoxycarbonyl)derivatives 3e and 3f, respectively.These compounds behave similarly to the corresponding lactone, 5,5-dimethyl-2(5H)-furanone, studied previously.