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Monoalkylation, glycine Schiff base

Monoalkylation of Schiff Bases Derived from Glycine... [Pg.9]

Asymmetric Monoalkylation of Glycine Ester Schiff Bases... [Pg.71]

The requisite aldimine Schiff base 21 can be readily prepared by the simple imine formation between glycine tert-butyl ester and p-chlorobenzaldehyde in MeOH at room temperature, with the aid of MgS04. The asymmetric monoalkylation of 21 was... [Pg.83]

In 1978, O Donnell and coworkers developed the benzophenone imines of glycine alkyl esters 4 as glycine anion equivalents, which have been found to be perfed to use in the phase-transfer catalysis [10]. An essential feature of this reaction system lies in the selective mono substitution of the starting Schiff base, the O Donnell substrate 4. This can be possible because of the significant difference in acidity of a-hydrogen between starting substrate 4 p/C,(DMSO) 18.7 (R=Et)] and a-monosubstituted produd S p/C,(DMSO) 22.8 (R=Et, E = Me), 23.2 (R=Et, E = CH2Ph)] [11]. This dramatic acidity difference makes it possible for selective formation of only monoalkylated product without concomitant production of undesired dialkylated produd or racemization. [Pg.136]

O Donnell reported the asymmetric alkylation of the Schiff base of tert-h xty glycinate using TV-benzylcinchonium chloride (Scheme 3.26b, [151]). This process, which works for methyl, primary alkyl, allyl, and benzyl halides (Table 3.11), is noteworthy because the substrate is acyclic and because monoalkylation is achieved without racemization under the reaction conditions. The observed chirality sense may be rationalized by assuming an jE fO)-enolate and Jt-stacking of the benzophenone rings of the enolate above the quinoline ring on the catalyst, and approach of the electrophile as before. [Pg.102]


See other pages where Monoalkylation, glycine Schiff base is mentioned: [Pg.83]    [Pg.130]   
See also in sourсe #XX -- [ Pg.9 , Pg.10 , Pg.11 , Pg.12 , Pg.13 , Pg.14 , Pg.15 , Pg.16 , Pg.17 , Pg.18 ]




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