Pyrroles with primary amine hydrochlorides

A versatile approach to 2-CF3-pyrroles was elaborated using dihydrofurans as masked 1,4-dicarbonyl compounds. Condensation of the dihydrofurans 261 with primary amine hydrochlorides gave the corresponding N-snbstituted pyrroles 262 in good yields [89]. 

A novel Mannich reaction between A -alkoxycarbonylpyrroles 739, formaldehyde, and primary amine hydrochlorides catalyzed by Y(OTf)3 gave a monoaminoalkylation product 741 some times in good yield (14-81%) in aqueous media (Scheme 146) <2001TL461>. When formaldehyde was replaced by acetaldehyde or benzaldehyde, no reaction occurred. There was no formation of the 2,7-diazabicyclo[2.2.1]hept-5-ene 740 (through the aza-Diels-Alder reaction of an N-protected pyrrole with an aldehyde and amine salts by catalysis with triflate). 

The mycinose moiety of tylosin can be specifically removed under mild conditions by oxidation of the free hydroxy-group of the sugar in the otherwise protected antibiotic to the corresponding glycos-4-ulose, which with a primary amine hydrochloride is degraded to a pyrrole derivative, liberating the aglycone, Selective A-acylation of kanamycin A has been studied, and conditions found for the preferential formation of the mono-6 -A-acyl or the 3-A-acyl derivative. " Base treatment of 3 -chloro-3 -deoxy-pseudotrisaccharides derived... 

The 2H- and 3Af-pyrrolium cations are essentially iminium ions and as such are electrophilic they play the key role in polymerisation (see 16.1.8) and reduction (16.7) of pyrroles in acid. In the reaction of pyrroles with hydroxylamine hydrochloride, which produces ring-opened 1,4-dioximes, it is probably the more reactive 37f-pyrrolium cation that is the starter. Primary amines, RNH2, can be protected, by conversion into l-R-2,5-dimethylpyrroles (16.16.1.1), recovery of the amine being by way of this reaction with hydroxylamine." ... 

Hydroxylamine hydrochloride and sodium carbonate in ethanol with pyrroles lead to dioximes of 1,4-dicarbonyl compounds [109], for example, 2,5-dimethyl-N-alkylpyrroles give the dioxime of hexane-2,5-dione (32) and primary amines R-NH2 ... 

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