New synthesis of 5,5-dimethyl-3-oxo-4,5-dihydro-3H-pyrrole 1-oxide

• Published in: Russian journal of organic chemistry Vol. 46; no. 7; pp. 1049 - 1052
• Main Authors: Golubev, V. A, Sen', V. D
• Format: Journal Article
• Language: English
• Published: Dordrecht Dordrecht : SP MAIK Nauka/Interperiodica 01-07-2010; SP MAIK Nauka/Interperiodica
• Subjects: Chemistry; Chemistry and Materials Science; Organic Chemistry; Sodium Perchlorate; Spin Trap; Nitroxyl Radical; Zinc Dust; Acidity Constant
• ISSN: 1070-4280; 1608-3393
• DOI: 10.1134/S1070428010070146

A procedure has been developed for the synthesis of 5,5-dimethyl-3-oxo-4,5-dihydro-3H-pyrrole 1-oxide via oxidation of 2,2,6,6-tetramethyl-4-oxopiperidine 1-oxyl with chlorine in aqueous sodium perchlorate and subsequent ring contraction in the resulting 2,2,6,6-tetramethyl-1,4-dioxopiperidinium perchlorate in dilute perchloric acid. The relative rates of proton exchange between the CH₂ and CH groups in the title compound were determined by ¹H NMR spectroscopy in D₂O, and the acidity constant was estimated on the basis of the dependence of the UV spectrum upon pH (pK a = 13.2).