1. Selective monosulfoxidation of tetrathiafulvalenes into chiral TTF-sulfoxides
Marcos Chas, François Riobé, Raquel Sancho, Cristina Minguíllon, Narcis Avarvari Chirality. 2009 Oct;21(9):818-25. doi: 10.1002/chir.20692.
Four inner tetrathiafulvalene-sulfoxides have been synthesized upon reaction of tetrathiafulvalene (TTF), tetramethyl-tetrathiafulvalene (TMTTF), tetrakis (thiomethyl)-tetrathiafulvalene (TMT-TTF), and bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF) with enantiopure (+) or (-)-(8,8-dichlorocamphorylsulfonyl)-oxaziridine as oxidizing agent. Chiral HPLC studies indicate very weak enantioselectivities for TTF-SO 3 and TMTTF-SO 4, formation of racemic mixture in the case of TMT-TTF-SO 5, and a rather good selectivity, up to 44% ee, in the case of BEDT-TTF-SO 1. The solid state structures of TMTTF-SO 4 and TMT-TTF-SO 5 have been determined by single crystal X-ray diffraction. Both compounds crystallize as racemates in the centrosymmetric triclinic space group P-1. Theoretical calculations at DFT/B3LYP/6-31+G* level afford optimized geometries in good accordance with the experimental structures and emphasize the participation of the chiral sulfoxide group in HOMO and LUMO. Time-dependent DFT calculations corroborated with electronic circular dichroism spectra allow the assignment of the absolute configuration (R) for the major enantiomer of 1 when the (+)-sulfonyl-oxaziridine is used as oxygen transfer reagent. Preliminary semipreparative HPLC separation provided enantioenriched fractions up to 63% ee.
2. Chemoenzymatic Deracemization of Chiral Sulfoxides
Vladimír Nosek, Jiří Míšek Angew Chem Int Ed Engl. 2018 Jul 26;57(31):9849-9852. doi: 10.1002/anie.201805858. Epub 2018 Jun 29.
The highly enantioselective enzyme methionine sulfoxide reductase A was combined with an oxaziridine-type oxidant in a biphasic setup for the deracemization of chiral sulfoxides. Remarkably, high ee values were observed with a wide range of substrates, thus providing a practical route for the synthesis of enantiomerically pure sulfoxides.
3. Macrocyclic and polymeric oxaziridine-derivatives
Marcus Dickmeis, Hakan Cinar, Helmut Ritter Macromol Rapid Commun. 2013 Feb 12;34(3):263-8. doi: 10.1002/marc.201200706. Epub 2013 Jan 11.
Macrocyclic and polymeric imines 5,5' and 6,6' are obtained in excellent yields by template-free polycondensation of 1,6-bis(4-formylbenzoyloxy)hexane (1) with commercially available 4,4'-methylene-bis(cyclohexylamine) (2) and with bis(2-amino-2-methylprop-1-yl)adipate dihydrochloride (4), respectively. The degree of macrocyclization during imine synthesis strongly depends on the diamine. Matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF) mass spectrometry analysis and gel permeation chromatography (GPC) measurements show that (2) leads to more macrocyclic adducts than (4). The subsequent meta-chloroperoxybenzoic acid oxidation of polyimines 5,5' and 6,6' ($ \bar M_{\rm n} $ = 1650-11 200 g mol(-1) , $ \bar M_{\rm w} $ = 3800-27 350 g mol(-1) ) yields the corresponding polyoxaziridines 7,7' and 8,8' consisting of macrocyclic and linear polymeric structures ($ \bar M_{\rm n} $ = 1750-8050 g mol(-1) , $ \bar M_{\rm w} $ = 3250-15 800 g mol(-1) ). The synthesized polyoxaziridines are relatively stable and storable at room temperature.
