Vilsmeier–Haack reaction with succinamidals. A convenient synthesis of 5-chloropyrrole-2-carboxaldehydes and 5-chloropyrrole-2,4-dicarboxaldehydes

Abstract

It is shown that the reaction of N-alkylsuccinamidals (2) with the Vilsmeier–Haack reagent derived from DMF and phosphorus oxychloride can be controlled to preferentially produce either 5-chloropyrrole-2-carboxaldehydes (8) or 5-chloropyrrole-2,4-dicarboxaldehydes (9). The corresponding N-unsubstituted aldehydes are obtained when N-tert-butoxycarbonylsuccinamidal (11) is the substrate in the above reactions. Keywords: Vilsmeier–Haack reaction, succinamidals, 5-chloropyrrole-2-carboxaldehydes, 5-chloropyrrole-2,4-dicarboxaldehydes.

Acid-catalysed formation of tricyclic N,S-acetals in imidazolinone series based on the use of the unprecedented N-acyliminium ion cascade reaction involving transposition, heterocyclisation and π-cyclisation

“…in analogy to reports by Hough et al 9 To avoid the poor solubility of the imide 3a, in addition to the laborious work-up encountered during this process, we have anticipated that the conversion of 3a to the N-Boc protected imide 4a could offer a better result by increasing the solubility of hydroxyimidazolidinone substrate. So, treatment of 4a, obtained by standard N-protection with the tandem Boc 2 O-DMAP (quantitative yield), 10 under our reduction protocol (conditions (v)) gave 5-hydroxyimidazolidinone 5a (R 3 = H, R 4 = Boc) in 89% yield. Analogous procedures (3 → 4 → 5) were used successfully to afford elegantly 5c-i (R 4 = Boc), with other substituents on different positions of the aromatic ring (see Table 1).…”

Synthesis of 5-Substituted 2-Pyrrolidinones by Coupling of Organozinc Reagents with Cyclic N-Acyliminium Ions

“…has been previously reported in moderate yield. 22 However, when the reaction was carried out on gram scale, a mixture of N-Boc-5-hydroxy-2-pyrrolidinone (2c) (24%) along with the over-reduction product 3c (30%) was obtained ( Table 1, entry 4).…”

Deoxypegan-1-one derivatives. synthesis and borohydride reduction of 3-[(E)-arylmethylidene]-3,9-dihydropyrrolo[2,1-b]quinazolin-1(2H)-ones

“…It is well known [26,27] that N-substituted succinimides are readily reduced by NaBH 4 to 5-hydroxy-2-pyrrolidinone derivatives. Obviously, for derivatives of 2, the reaction proceeds along this same pathway and forms 3-[(E)-arylmethylidene]-1,2,3,9-tetrahydropyrrolo[2,1-b]quinazolin-1-ols (8a-d).…”