Synthesis of 3-Diazopyrrolidin-2-ones

Abstract

In the present work we succeeded in developing a procedure for the synthesis of previously unknown 3-diazopyrrolidin-2-ones from 3-aminopyrrolidin-2-one (I) and 5-amino-3-exo-azatricyclo[5.2.1.0 2,6 ]decan-4one (II). Stable 3-diazodihydropyrroles or 3-diazopyrrolidinediones have been reported [6–8], but attempts to obtain 3-diazopyrrolidin-2-one or its alkyl-substituted derivatives were unsuccessful [14]. In particular, diazotization of 5-amino-3-exo-azatricyclo[5.2.1.0 2,6 ]decan-4-one led to a mixture of isomeric 3-acetoxypyrrolidinones [14]. We have found that heating of a solution of 3-aminopyrrolidin-2-one (I) or 5-amino-3-exo-azatricyclo[5.2.1.0 2,6 ]decan-4-one (II) with isopentyl nitrite in chloroform in the presence of ~15 mol % of glacial acetic acid gives 3-diazopyrrolidin-2-one (III) and 5-diazo-3-exo-azatricyclo[5.2.1.0 2,6 ]decan-4-one (IV) in 36 and 65% yield, respectively. We failed to isolate diazo lactam III as individual substance; it decomposed in diethyl ether even at room temperature to produce a mixture of compounds which were difficult to identify. Therefore, the formation of III was proved by trapping it with triphenylphosphine. The latter reacted with 3-diazopyrrolidin-2-one (III) to give stable crystalline phosphazene V. In the synthesis of diazo lactam III, acetic acid was neutralized with solid NaHCO3, for a saturated aqueous solution of NaHCO3