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Open AccessArticle

2-Unsubstituted Imidazole N-Oxides as Novel Precursors of Chiral 3-Alkoxyimidazol-2-ylidenes Derived from trans-1,2-Diaminocyclohexane and Other Chiral Amino Compounds

1
Department of Organic and Applied Chemistry, University of Łódź, Tamka 12, PL-91-403 Łódź, Poland
2
Department of Organic Chemistry, Wrocław University of Technology, Wyspiańskiego 27, PL-50-370 Wrocław, Poland
3
Justus Liebig University, Institute of Organic Chemistry, Heinrich-Buff-Ring 17, D-35392 Giessen, Germany
4
Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
*
Author to whom correspondence should be addressed.
Dedicated to Professor Marek Zaidlewicz (Toruń) on the occasion of his 80th birthday.
Academic Editors: Zbigniew Czarnocki and Joanna Szawkało
Molecules 2019, 24(23), 4398; https://doi.org/10.3390/molecules24234398
Received: 19 November 2019 / Revised: 28 November 2019 / Accepted: 29 November 2019 / Published: 2 December 2019
(This article belongs to the Special Issue Stereochemistry in Action)
‘Desymmetrization’ of trans-1,2-diaminocyclohexane by treatment with α,ω-dihalogenated alkylation reagents leads to mono-NH2 derivatives (‘primary-tertiary diamines’). Upon reaction with formaldehyde, these products formed monomeric formaldimines. Subsequently, reactions of the formaldimines with α-hydroxyiminoketones led to the corresponding 2-unsubstituted imidazole N-oxide derivatives, which were used here as new substrates for the in situ generation of chiral imidazol-2-ylidenes. Upon O-selective benzylation, new chiral imidazolium salts were obtained, which were deprotonated by treatment with triethylamine in the presence of elemental sulfur. Under these conditions, the intermediate imidazol-2-ylidenes were trapped by elemental sulfur, yielding the corresponding chiral non-enolizable imidazole-2-thiones in good yields. Analogous reaction sequences, starting with imidazole N-oxides derived from enantiopure primary amines, amino alcohols, and amino acids, leading to the corresponding 3-alkoxyimidazole-2-thiones were also studied. View Full-Text
Keywords: carbene sulfurization; chiral compounds; chiral nucleophilic carbenes; imidazole N-oxides; imidazole-2-thiones; N-alkoxyimidazolium salts carbene sulfurization; chiral compounds; chiral nucleophilic carbenes; imidazole N-oxides; imidazole-2-thiones; N-alkoxyimidazolium salts
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Mlostoń, G.; Celeda, M.; Jasiński, M.; Urbaniak, K.; Boratyński, P.J.; Schreiner, P.R.; Heimgartner, H. 2-Unsubstituted Imidazole N-Oxides as Novel Precursors of Chiral 3-Alkoxyimidazol-2-ylidenes Derived from trans-1,2-Diaminocyclohexane and Other Chiral Amino Compounds. Molecules 2019, 24, 4398.

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