- Desymmetrization of prochiral diaryl sulfoxides by an asymmetric sulfoxide-magnesium exchange
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The first desymmetrizations of prochiral diaryl sulfoxides 1 by an asymmetric sulfoxide-magnesium exchange reaction are reported. The respective substrate (1), iPr2Mg, and the dilithium salt of (S)-BINOL (which was prepared in situ) provided (S)-configured aryl isopropyl sulfoxides 2 in up to 91 % yield and with up to 91 % ee. (S)-BINOL was re-isolable in 98 % yield. Copyright
- Hampel, Thomas,Ruppenthal, Simon,Saelinger, Daniel,Brueckner, Reinhard
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supporting information; experimental part
p. 3136 - 3140
(2012/05/20)
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- Synthesis of 1-(1-arylsulfanylalkyl)indoles and 2,2-bis[1-(1-arylsulfanylalkyl)indol-3-yl]propanes by acid-catalyzed reactions of indoles with aryl vinyl sulfides
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We report a facile synthesis of 1-(1-arylsulfanylalkyl)indoles and 2,2-bis[1-(1-arylsulfanylalkyl)indol-3-yl]propanes under mild conditions. Thus, treatment of 3-substituted indoles with aryl vinyl sulfides in dichloromethane at room temperature in the presence of a catalytic amount of (±)-camphor-10-sulfonic acid yields the former indole derivatives in moderate to fair yields. 3-Nonsubstituted indoles can be transformed into the latter indole derivatives in satisfactory yields on treatment with excess aryl vinyl sulfides in the presence of a catalytic amount of the acid under similar conditions.
- Kobayashi, Kazuhiro,Shirai, Yuu,Fukamachi, Shuhei,Konishi, Hisatoshi
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body text
p. 433 - 439
(2010/09/05)
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- Enantioselective inclusion of chiral alkyl aryl sulfoxides in a supramolecular helical channel consisting of an enantiopure 1,2-amino alcohol and an achiral carboxylic acid
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The enantioselective clathrate formation of alkyl aryl sulfoxides 4 was achieved with dissymmetric one-dimensional helical channels created in two-component hosts consisting of (1R,2S)-2-amino-1,2-diphenylethanol 1 and an achiral carboxylic acid, p-tert-butylbenzoic acid 2, or 2-anthraquinonecarboxylic acid 3. X-ray crystallographic analyses showed that the host framework (1R,2S)-1·3 in the single crystal of a clathrate with methyl p-methylphenyl sulfoxide 4n [(1R,2S)-1·3·4n (single)] maintained a supramolecular helical array as those of the solvent-included single crystals (1R,2S)-1·3·EtOH(single) and (1R,2S)-1·3·H2O·THF(single), while the guest 4n molecules were highly disordered. Moreover, the X-ray powder diffraction pattern of (1R,2S)-1·3·4n(clathrate) obtained through the clathrate formation demonstrated that the molecular arrangements of (1R,2S)-1, 3, and 4n were not the same as those which appeared in (1R,2S)-1·3·4n(single); the channel was enlarged. These results are consistently explained by assuming the dynamic motion of the framework (1R,2S)-1·3 to achieve widely applicable clathrate formation.
- Kobayashi, Yuka,Soetrisno,Kodama, Koichi,Saigo, Kazuhiko
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p. 295 - 301
(2008/09/19)
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- Aryl sulfoxides via palladium-catalyzed arylation of sulfenate anions
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(Chemical Equation Presented) Palladium-catalyzed arylation of sulfenate anions generated from β-sulfinyl esters can take place under biphasic conditions. This hitherto unknown reaction provides a simple, mild, and efficient route to aryl sulfoxides in good yields. The development of a new pseudo-domino type I procedure involving a sulfinylation followed by a Mirozoki-Heck coupling is also described.
- Maitro, Guillaume,Vogel, Sophie,Prestat, Guillaume,Madec, David,Poli, Giovanni
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p. 5951 - 5954
(2007/10/03)
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- Mechanism of the oxidation of aromatic sulfides catalysed by a water soluble iron porphyrin
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The oxygen atom transfer-electron transfer (ET) mechanistic dichotomy has been investigated in the oxidation of a number of aryl sulfides by H2O2 in acidic (pH 3) aqueous medium catalysed by the water soluble iron(III) porphyrin 5,10,15,20-tetraphenyl-21H,23H-porphine-p,p′,p″,p?-tetrasulfo nic acid iron(III) chloride (FeTPPSCl). Under these reaction conditions, the iron-oxo complex porphyrin radical cation, P+ Fe(IV)=O, should be the active oxidant. When the oxidation of a series of para-X substituted phenyl alkyl sulfides (X = OCH3, CH3, H, Br, CN) was studied the corresponding sulfoxides were the only observed product and the reaction yields as well as the reactivity were little influenced by the nature of X as well as by the bulkiness of the alkyl group. Labelling experiments using H2 18O or H218O2 clearly indicated that the oxygen atom in the sulfoxides comes exclusively from the oxidant. Moreover, no fragmentation products were observed in the oxidation of a benzyl phenyl sulfide whose radical cation is expected to undergo cleavage of the β C-H and C-S bonds. These results would seem to suggest a direct oxygen atom transfer from the iron-oxo complex to the sulfide. However, competitive experiments between thioanisole (E° = 1.49 V vs. NHE in H2O) and N,N-dimethylaniline (E° = 0.97 V vs. NHE in H2O) resulted in exclusive N-demethylation, whereas the oxidation of N-methylphenothiazine (10, E° = 0.95 V vs. NHE in CH3CN) and N,N-dimethyl-4-methylthioaniline (11, E° = 0.65 V vs. NHE in H2O) produced the corresponding sulfoxide with complete oxygen incorporation from the oxidant. Since an ET mechanism must certainly hold in the reactions of 10 and 11, the oxygen incorporation experiments indicate that the intermediate radical cation, once formed, has to react with PFe(IV)=O (the reduced form of the iron-oxo complex which is formed by the ET step) in a fast oxygen rebound. Thus, an ET step followed by a fast oxygen rebound is also suggested for the other sulfides investigated in this work.
- Baciocchi, Enrico,Gerini, Maria Francesca,Lanzalunga, Osvaldo,Lapi, Andrea,Lo Piparo, Maria Grazia
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p. 422 - 426
(2007/10/03)
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- Chemistry of oxaziridines. 17. N-(phenylsulfonyl)(3,3-dichlorocamphoryl)oxaziridine: A highly efficient reagent for the asymmetric oxidation of sulfides to sulfoxides
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The synthesis, structure, and enantioselective oxidations of a new chiral N-sulfonyloxaziridine 12c [3,3-dichloro-1,7,7-trimethyl-2'-(phenylsulfonyl)spiro[bicyclo[2.2.1]heptane-2, 3'-oxaziridine]] are reported. This oxidant, which exhibits remarkably high and predictable ee's for the enantioselective oxidation of prochiral sulfides to sulfoxides, is prepared in three steps from (+)- or (-)-camphor in 50% overall yield. Steric effects are primarily responsible for the molecular recognition and are predictable using a simple active-site model where the nonbonded interactions between the RL and RS groups of the sulfide (RL-S-RS) and the active-site surface are minimized in a planar transition-state structure. The fact that alkyl aryl sulfides give high ee's in nonpolar solvents suggests that there is also a stereoelectronic component to the molecular recognition. High ee's (>90%) are anticipated for those sulfides where the difference in size of the groups directly bonded to the sulfur atom is large, i.e., aryl, tert-butyl vs CH2R (R = H, alkyl, benzyl, etc). The X-ray structure and studies with the dihydro, difluoro, and dibromo oxaziridines 12a, 12b, and 12d reveal that the exceptional enantioselectivities displayed by 12c are a consequence of a molecular cleft or groove, defined by the oxaziridine chlorine atoms and phenylsulfonyl group, on the active-site surface.
- Davis, Franklin A.,Thimma Reddy,Han, Wei,Carroll, Patrick J.
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p. 1428 - 1437
(2007/10/02)
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