- Thioamide-substituted cinchona alkaloids as efficient organocatalysts for asymmetric decarboxylative reactions of MAHOs
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A new class of thioamide-substituted cinchona derivatives is reported. A convergent and practical approach was developed to insert the thioamide functional group onto the cinchonidine from readily available dithioesters. These organocatalysts were effective in asymmetric decarboxylative Mannich and protonation reactions of α-amido-substituted malonic acid half oxyesters (MAHOs), affording α,β- and α-amino acid derivatives, respectively, in good yields and stereoselectivities.
- Singjunla, Yuttapong,Pigeaux, Morgane,Laporte, Romain,Baudoux, Jér?me,Rouden, Jacques
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- Catalyst development for organocatalytic hydrosilylation of aromatic ketones and ketimines
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A new family of Lewis basic 2-pyridyl oxazolines have been developed, which can act as efficient organocatalysts for the enantioselective reduction of prochiral aromatic ketones and ketimines with trichlorosilane, a readily available and inexpensive reagent. 1-Isoquinolyl oxazoline, derived from mandelic acid, was identified as the most efficient catalyst of the series, capable of delivering high enantioselectivities in the reduction of both ketones (up to 94% ee) and ketimines (up to 89% ee).
- Malkov, Andrei V.,Stewart-Liddon, Angus J. P.,McGeoch, Grant D.,Ramirez-Lopez, Pedro,Kocovsky, Pavel
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p. 4864 - 4877
(2012/07/28)
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- Dithiocarboxylic Acids, Dithiocarboxylic Esters, or Thiocarboxylic Amides by Reaction of Methylene-active Chloromethyl Compounds with Sulfur
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With a mixture of sulfur and amine in DMF at room temperature halomethyl compounds (1,5-10) can be oxidized to give thiocarboxylic acids (2,11-16) and their derivatives (3,4,17-35).We studied this reaction in detail especially with chloroacetic derivatives (11-15) or chloromethyl heterocycles (16) formally derived from chloroacetic acid.The resulting thiooxalic acid derivatives (11-27) represent activated acids and very useful C2-synthons, especially for the synthesis of heterocycles.Oxidation in the presence of triethylamine leads to dithiocarboxylates (11-16) which can be alkylated to dithioesters (17-27) in high yields.As a rule, with different primary and secondary amines instead of tertiary amines these dithiocarboxylates or dithiocarboxylic esters can be transformed already at low temperatures to thioamides (28-35).
- Thiel, W.,Mayer, R.
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p. 243 - 262
(2007/10/02)
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