- An organocascade approach to α,α-chlorofluoroalcohols
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Abstract Fluorinated, tetrasubstituted, carbon stereocenters are challenging to install enantioselectively. gem-Chlorofluoro compounds contain a fluorinated, tetrasubstituted stereocenter, and are an entrée into other such compounds. We report herein the first catalytic, enantioselective method to prepare gem-chlorofluoro compounds from unfunctionalized aldehydes. This one-pot method precludes the isolation of volatile and/or reactive α-haloaldehyde intermediates.
- Hayes, Montgomery D.,Rodríguez-Alvarado, Melanie,Brenner-Moyer, Stacey E.
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- Trichloromethanesulfonyl chloride: A chlorinating reagent for aldehydes
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Trichloromethanesulfonyl chloride (CCl3SO2Cl), a commercially available reagent, has been found to perform efficiently in the α-chlorination of aldehydes, including its catalytic asymmetric version, under very mild reaction conditions. Under our reaction conditions, this compound outperforms typical chlorinating reagents for organic synthesis, facilitates workup and purification of the product, and minimizes the formation of toxic, chlorinated organic waste.
- Jimeno, Ciril,Cao, Lidong,Renaud, Philippe
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p. 1251 - 1255
(2016/02/19)
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- Shorter and easier syntheses of Di-tert-butylketene and related gem-Di-tert-butyl compounds
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The ketene tBu2C=C=O is prepared from tBu2C=O in three steps (performable as a two-stage operation) through elimination of HCl from the intermediate product tBu2CCl-CH=O. The acid tBu 2CH-CO2H, obtainable in two, three, or four preparative stages from tBu2C=O, adds slowly to the ketene to produce the anhydride (tBu2CH-CO)2O. Elemental lithium together with ClSiMe3 converts tBu2CCl-CH=O into tBu2C=CH- OSiMe3, which is a durable precursor of tBu2CH-CH=O, making this aldehyde easily and cheaply available from tBu2C=O. By exclusion of alternative mechanistic possibilities, the reduction of tBu 2CCl-CH=O by tBuMgCl is shown to involve at least one single-electron transfer, leading to the enolate tBu2C=CH-OMgCl, which can be converted into tBu2CH-CH=O (three steps from tBu2C=O) or into tBu2C=CH-OSiMe3. Hydride transfer from NaBH 4 to tBu2CCl-CH=O affords tBu2CCl-CH 2OH, the transformations of which provide an entertaining set of SN1-type reactions. Several other examples of carbenium-type behavior are encountered in this gem-tBu2 system; they are attributed to steric congestion, which also impedes bond rotations in the anhydride and in two esters. A convenient route to tBu2CH-C≡N (five steps from tBu2C=O) uses the conversion of tBu2C=CH-OSiMe3 into tBu2CH-CH=NOH. The slow thermal (Z)/(E) equilibration of tBu2CH-NH-CH=O reveals the ranking of ecliptic repulsions as H 3C 2CH. Copyright
- Knorr, Rudolf,Hennig, Karsten-Olaf,Schubert, Bernhard,Boehrer, Petra
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p. 6651 - 6664
(2011/02/26)
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- Synthesis, fragmentations and rearrangements of 3-(1-haloalkyl) oxaziridines
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A variety of new 3-(1-haloalkyl)oxaziridines was synthesized by oxidation of α-chloro-, α-bromo-, α,α-dichloro-, α,α-dibromo- and α,α,α-trichloroaldimines with meta-chloroperbenzoic acid. Attempts to induce dehydrohalogenation into the elusive methyleneoxaziridines were unsuccessful. However, presumptive evidence is presented that 2-t-butyl-3-(trichloromethyl)oxaziridine is dehydrochlorinated into a transient methyleneoxaziridine, which underwent valence isomerization into an intermediate iminooxirane, the latter being fragmented into t-butyl isocyanide. Various types of reactions of the title compounds are reported. Among others, 2-alkyl-3-(1-chloro-1-methyl) ethyloxaziridines rearranged with methyllithium into 2-(N-alkyl)aminoisobutyraldehydes.
- De Kimpe, Norbert,De Corte, Bart
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p. 7345 - 7362
(2007/10/02)
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- Control of Regioselectivity in the Addition of Sulphenyl Chlorides to 3,3-Dimethylbutyne (t-Butylacetylene) as a Method for Differential Functionalization of Triple Bonds
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Methanesulphenyl chloride and toluene-p-sulphenyl chloride react with 3,3-dimethylbutyne to give regio- and stereo-specifically (E)-1-chloro-3,3-dimethyl-2-methylthiobut-1-ene (3a) and (E)-1-chloro-3,3-dimethyl-2-p-tolylthiobut-1-ene (3b). trans-cis-Acid-
- Capozzi, Giuseppe,Caristi, Corrado,Lucchini, Vittorio,Modena, Giorgio
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p. 2197 - 2202
(2007/10/02)
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