N-Acylazinium Salts:  A New Source of Iminium Ions for Ugi-Type Processes

Abstract

A multicomponent reaction involving the interaction of azines (quinolines, isoquinolines, and phenanthridine) with activating agents (chloroformates, acid halides, and sulfonyl halides), isocyanides, and water is described. The products of this process, alpha-carbamoylated-1,2-dihydroazines, are the result of the addition of the isocyanide partner to the N-acylazinium salt formed in situ. This represents a new source of iminium ion equivalents for Ugi-type reactions.

Hydrazinopeptide Motifs Synthesized via the Ugi Reaction: An Insight into the Secondary Structure

“…3 However, finding workable surrogates for the iminium component, the formation of which from the amine and carbonyl compounds under acidic catalysis triggers the Ugi reaction, appears more challenging as one finds only a handful of examples of this approach in the literature. Among the examples reported are the successful uses of various hydrazones 4 and oximes, 5 and more recently published methodologies involving N-acylazinium 6 and N-fluoropyridinium 7 salts as less obvious substitutes for the iminium reaction partner for an isocyanide.…”

“…Upon solvent change from deuterated dimethylsulfoxide (DMSO-d 6 ) to chloroform-d (CDCl 3 ), one can pinpoint those protons that are indeed involved in the intramolecular hydrogen bond. 18 Indeed, as can be seen from Table 3, using DMSO-d 6 as a solvent capable of accepting a hydrogen bond from the solute causes the downfield shift of the acidic, amide-type protons H 1 and H 2 in reference fragments 10 and 11, respectively ( Figure 2).…”

“…Upon solvent change from deuterated dimethylsulfoxide (DMSO-d 6 ) to chloroform-d (CDCl 3 ), one can pinpoint those protons that are indeed involved in the intramolecular hydrogen bond. 18 Indeed, as can be seen from Table 3, using DMSO-d 6 as a solvent capable of accepting a hydrogen bond from the solute causes the downfield shift of the acidic, amide-type protons H 1 and H 2 in reference fragments 10 and 11, respectively ( Figure 2). 19 Roughly the same downfield shift of the 1 H NMR spectroscopic signals was observed for the N b -H 1 protons of compounds 4 compared to those of 10, but this was not the case for the terminal amide protons H 2 , which were significantly less sensitive to the solvent change than the corresponding H 2 protons in 11.…”

Simple and one-pot synthesis of new heterocyclic compounds in three-component reactions between isoquinoline or phenanthridine and acetylenic esters in the presence of N-heterocycles or 1,3-dicarbonyl compounds

“…24 Isoquinoline is also present in various natural products such as cryptaustoline and cryptowoline. 25 They are known to exhibit various biological activities [26][27][28][29][30][31][32][33][34] such as antileukaemic, 35 tubulin polymerization inhibitory 36 and anti-tumour activities. 37 As previously reported, 38 reaction between phenanthridine and two mol equivalents of dimethyl acetylenedicarboxylate, leads to the…”

First Example of Functionalization of Activated Quinolines by Indoles Using CeCl3·7H2O

“…Addition of isocyanides to Nacylazinium salts has been reported as an alternative process for Reissert synthesis via Ugi-type reaction. 11 In continuation of our recent work on aza-aromatics 12 activated by acyl chlorides, we turned our attention to addition of the indole moiety to quinolines. In this article, we wish to disclose a mild and efficient method for the synthesis of 2-(3-indolyl)-1,2-dihydroquinolines using CeCl 3 ·7H 2 O as the novel catalyst.…”