223269-01-0Relevant academic research and scientific papers
Stereoselective alkylation of chiral 2-imidoylphenols with organolithium reagents: Synthesis of enantiopure 2-aminoalkylphenols
Cimarelli, Cristina,Palmieri, Gianni,Volpini, Emanuela
, p. 1200 - 1206 (2007/10/03)
In this paper the addition of organolithium reagents to chiral imidoylphenols to prepare enantiopure phenolic Mannich-type bases is described. The experimental data show that this kind of imine is surprisingly reactive toward organolithium reagents, differently from classical imines, and does not need any Lewis acid or base activation. Moreover, interesting results have been obtained with aldimines but more unusually with ketimines. This reaction results in high yields and diastereoselectivities and allows the preparation of aminophenols quaternary at the C-1 carbon atom, which cannot be prepared with the methods available till now. The sense of asymmetric induction has been explained and confirmed in agreement with the results previously obtained by hydride reduction of the same substrates. In some cases this procedure is complementary to the reductive one, allowing the preparation of the diastereomers less abundant in the reduction. The reaction allows the synthesis of one or the other of the two diastereomers, choosing the opportune starting imidoylphenol and the organolithium reagent.
Asymmetric reduction of enantiopure imines with zinc borohydride: Stereoselective synthesis of chiral amines
Cimarelli, Cristina,Palmieri, Gianni
, p. 2555 - 2563 (2007/10/03)
The first application of zinc borohydride in the reduction of enantiopure imines for the stereoselective preparation of both the enantiomers of secondary amines is described. A possible explanation of the stereoselectivity and of the reaction mechanism is
Synthesis of enantiopure o-hydroxybenzylamines by stereoselective reduction of 2-imidoylphenols: Application in the catalytic enantioselective addition of diethylzinc to aldehydes
Palmieri, Gianni
, p. 805 - 811 (2007/10/03)
Enantiopure o-hydroxybenzylamines 2a-i were synthesized by diastereoselective reduction of the 2-imidoylphenols (R)-1a-i. Conformational analysis enabled the assignment of the absolute configurations of compounds 2a-i. The accessible o-hydroxybenzylamine (R,R)-2h serves as an effective catalyst precursor for highly enantioselective addition of diethylzinc to aliphatic and aromatic aldehydes. This pathway represents a practical and operationally very simple methodology for the enantioselective synthesis of both the enantiomers of secondary alcohols 7a-f.
