- Cobalt catalysed hydro-sulfenylation of Michael acceptors
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The reaction of certain types of Michael accepters, limited to those having methylene groups, with a mixture of diphenyl disulfide and phenyl silane, under the influence of 10% of the cobalt catalyst, Co(eobe) 3, results in the formation of hydro-sulfenylated products, such as α-phenylthio carbonyl compounds, in moderate to good yields. The process involves intermediates having radical character, judging by the 5-exo-trig cyclisation product 21 observed in the reaction of α,β-unsaturated ester 20 having a suitable unsaturated side-chain.
- Friend, Christopher L.,Simpkins, Nigel S.,Anson, Michael,Polywka, Mario E. C.
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- Selectivity reversal during thia-Michael additions using tetrabutylammonium hydroxide: Operationally simple and extremely high turnover
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The use of tetrabutylammonium hydroxide as a novel and exceedingly efficient thia-Michael addition catalyst is herein described. This extremely simple methodology allows for the conjugate addition of a wide variety of mercaptan nucleophiles, and functions remarkably well with a very wide range of both classical and non-classical Michael acceptors. Contradistinctive to current literature reports, the use of this catalyst more efficiently promotes the addition of more basic thiols. This methodology is especially attractive and operationally simple, as it generally proceeds with only 1 mol% catalytic loading and without excess reagent, and the produced products typically require no purification. Georg Thieme Verlag Stuttgart New York.
- Nicponski, Daniel R.,Marchi, Jennifer M.
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supporting information
p. 1725 - 1730
(2014/07/08)
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- N-heterocyclic carbene catalyzed carba-, sulfa-, and phospha-Michael additions with NHC·CO2 adducts as precatalysts
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N-heterocyclic carbene catalyzed Michael additions have been revisited with 1,3-dialkyl- or 1,3-diarylimidazol(in)ium-2-carboxylates, that is, NHC·CO2 adducts, as the source of the free NHC catalysts in solution. Using these precatalysts, a number of efficient carba-, sulfa-, and phospha-Michael additions were achieved very conveniently, without the need for an external strong base to generate the NHC by deprotonation of an azolium salt. To further expand the scope of the procedure, some NHC-catalyzed sulfa-Michael/aldol organocascades were also investigated.
- Hans, Morgan,Delaude, Lionel,Rodriguez, Jean,Coquerel, Yoann
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p. 2758 - 2764
(2014/04/17)
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- Organocatalytic asymmetric synthesis of sulfoxides from sulfenic acid anions mediated by a cinchona -derived phase-transfer reagent
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Preliminary results concerning a conceptually novel route to chiral sulfoxides based on the asymmetric alkylation of sulfenate salts with alkyl halides mediated by a chiral phase-transfer catalyst are described. As a representative example, o-anisyl methyl sulfoxide was produced in 96% yield and with an enantiomeric excess of 58% using commercial cinchonidinium derivative 2a.
- Gelat, Fabien,Jayashankaran, Jayadevan,Lohier, Jean-Francois,Gaumont, Annie-Claude,Perrio, Stephane
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supporting information; experimental part
p. 3170 - 3173
(2011/08/06)
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- Reactivity in Z-Philic Displacements in α-Halogenosulfones
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Rates of Z-philic reactions in β-substituted α-bromosulfones have been measured; for displacement-protonation ρ* = 2.9, and isotope fractionation factors close to 2.4 demonstrate extensive C-protonation in the transition structure.
- Vernon, Adam,Stirling, Charles J. M.
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p. 1609 - 1610
(2007/10/02)
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- ARYL VINYL SULFONES AS THIOL PROTECTIVE GROUP
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Phenyl vinyl sulfone and p-tolyl isobutenyl sulfone are convenient reagents for protecting SH groups via the Michael adduct.Protection and deprotection can be achieved in high yields under mild basic conditions, in protic or aprotic solvents.
- Kuroki, Yoshiaki,Lett, Robert
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p. 197 - 200
(2007/10/02)
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