ChemInform Abstract: Synthesis and Photochemistry of 5,5‐Dimethyl‐1H‐pyrrol‐2(5H)‐one and of Some N‐Substituted Derivatives.

Abstract

(1 7.111.92)In two steps, 5,Sdimethyl-lH-pyrrol-2(5H)-one (3a) was prepared from 5,5-dimethylpyrrolidine-2,4-dione ( = dimethyltetramic acid; 4) in 71 % overall yield (Scheme 1 ) and further converted to N-substituted derivatives 3b-f viu acylation, alkylation, or methoxycarbonylation of its anion (Scheme 2). The substitutents on the N-atom exert a strong influence on the photochemical reactivity ([2 + 21 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( SH)-furanone, studied previously. Introduction. ~ In the course of our investigations on the photochemistry of cyclic a$-unsaturated carbonyl compounds [l][2], we had emphasized on the synthesis of several heteropentacyclic enones such as 1 and 2 with a geminal dimethyl group adjacent to the heteroatom to prevent tautomerization to a 2-or 3-hydroxy-substituted heterocycle. We had shown that both 3(2H)-and 2(5H)-furanones l a and 2a and 3(2H)-thiophenone l b exhibit photochemistry typical for cyclopent-2-enone itself [3-51 and that 2(5H)-thiophenones, e.g. 2b, behave differently in undergoing light-induced ring-opening reactions in hydroylic solvents [6] [7]. Finally, while lH-pyrro1-3(2H)-one l c is photoinert [8], the corresponding N-(ethoxycarbonyl) derivative Id again exhibits typical enone behavior [9]. We now report on a new -large-scale -synthesis of the 'missing link' in this

Recent Advances in the Synthesis of Cyclobutanes by Olefin [2 + 2] Photocycloaddition Reactions

“…692 Margaretha and coworkers studied the intermolecular [2 + 2] photocycloaddition chemistry of an N-unprotected γ-lactam, 5,5-dimethyl-lHpyrrol-2(5H)-one, and of its N-acyl derivatives. 693,694 In later work, the Ohfune group found a high facial diastereoselectivity in the [2 + 2] photocycloaddition reactions of chiral N-Boc 695 Similar results were recently found for substrate 385 in synthetic efforts toward cyclobutane-fused azanucleosides. 696 A chiral phenylethyl substituent at the nitrogen atom of an otherwise unsubstituted pyrrol-2(5H)-one resulted in only low facial diastereoselectivity.…”