2,5-disubstituted N,N'-alkylpiperazines represent an interesting target in organic synthesis both for pharmaceutical or agrochemical applications and as a promising class of ligands in coordination chemistry. We report here a microwave-enhanced synthesis of these compounds starting from non-activated N-alkyl aziridines in the presence of catalytic amounts of simple ammonium metallates. A remarkable TOF of 2787.9 h-1 has been observed in the case of [TBA]2[ZnI4] as the catalyst (catalyst loading 0.1 mol%) and with an almost complete selectivity (up to 97%) in favor of both diastereoisomers (meso and chiral form) of the target 2,5-disubstituted piperazines, obtained in 1:1 ratio. The two isomers are easily separated, because the meso form precipitates in pure from the reaction crude. A stereochemical investigation and the unprecedented isolation of 2,6-disubstituted N,N'-alkylpiperazines allowed us to shed light on the reaction mechanism.
Ammonium zincates as catalysts for the microwave‐enhanced synthesis of symmetric piperazines by regioselective opening of aziridines / M. Alberti, A. Dariol, N. Panza, G. Abbiati, A. Caselli. - In: CHEMISTRY - AN ASIAN JOURNAL. - ISSN 1861-4728. - 2024:(2024). [Epub ahead of print] [10.1002/asia.202400688]
Ammonium zincates as catalysts for the microwave‐enhanced synthesis of symmetric piperazines by regioselective opening of aziridines
M. AlbertiPrimo
;A. DariolSecondo
;N. Panza;G. AbbiatiPenultimo
;A. Caselli
Ultimo
2024
Abstract
2,5-disubstituted N,N'-alkylpiperazines represent an interesting target in organic synthesis both for pharmaceutical or agrochemical applications and as a promising class of ligands in coordination chemistry. We report here a microwave-enhanced synthesis of these compounds starting from non-activated N-alkyl aziridines in the presence of catalytic amounts of simple ammonium metallates. A remarkable TOF of 2787.9 h-1 has been observed in the case of [TBA]2[ZnI4] as the catalyst (catalyst loading 0.1 mol%) and with an almost complete selectivity (up to 97%) in favor of both diastereoisomers (meso and chiral form) of the target 2,5-disubstituted piperazines, obtained in 1:1 ratio. The two isomers are easily separated, because the meso form precipitates in pure from the reaction crude. A stereochemical investigation and the unprecedented isolation of 2,6-disubstituted N,N'-alkylpiperazines allowed us to shed light on the reaction mechanism.File | Dimensione | Formato | |
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Chemistry An Asian Journal - 2024 - Alberti - Ammonium zincates as catalysts for the microwave‐enhanced synthesis of(1).pdf
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asia202400688-s1-supportinginformation_piperazines_chemasianj.pdf
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