Preparação e utilização de amino catalisadores, derivados do glicerol e aminoácidos, em reações de formação de ligação carbono-carbono

Abstract

This work describes the attempt to prepare amino molecular catalysts from glycerol or D-mannitol and from natural amino acids. In addition, two ionic liquids derived from the amino acid L-histidine and glycerol were prepared, which were used together with their analogous (derivatives of L-valine, L-leucine, L-proline and Ltyrosine) as catalysts in reactions of carbon-carbon bond formation. To facilitate the discussion the catalysts were classified into three groups according to the nature of the amine present in the amino acid residue: Group a: primary amines: ionic liquids derived from L-valine, L-leucine and L-tyrosine; Group b: secondary amines: ionic liquids derived from L-proline and Group c: ionic liquids derived from L-histidine containing a primary amine and an imidazole ring. The carbon-carbon bond formation reactions selected for this study were the Morita-Baylis-Hillman reactions, aldol reaction and Michael reaction. These reactions were chosen because they are already used as a "model" in the development of aminocatalysts and because they have the spectroscopic characterization of their products well described in the literature. Parameters such as the catalytic capacity of the catalyst, enantio and diastereoselectivity of the products formed, the need to use other compounds as additives and finally, by how many catalytic cycles the catalyst would remain active. The Morita-Baylis-Hillman reaction was performed between methyl vinyl ketone and p-nitrobenzaldehyde. All ionic liquids were able to catalyze the reaction. However, the reactions whith ionic liquids derived from primary amines only occurred in the presence of imidazole, used as an additive. There is no other report in the literature of Morita-Baylis-Hillman reactions catalyzed by primary amines. Morita-Baylis-Hillman adducts were obtained in yields ranging from 36 to 89% and as racemic mixture. The best results were obtained when the ionic liquids derived from L-histidine were used as catalysts. The best reaction condition was used in the reaction of methyl vinyl ketone and different substituted aldehydes. In addition, the reaction mechanism was investigated by mass spectrometry coupled to capillary electrophoresis when the ionic liquids derived from L-histidine were used as catalysts. The aldol reaction was performed between cyclohexanone and pnitrobenzaldehyde. Again, all ionic liquids were able to catalyze the reaction. However, the best results were obtained when the ionic liquids derived from L-proline were used as catalysts. In this condition, the aldol addition product was obtained in 92% yield, diastereoisomeric ratio 1:4 (syn:anti) and enantiomeric excess 28:85% (syn:anti). The Michael reaction was performed between cyclohexanone, or propanone, and β-nitrostyrene. In this reaction, only the ionic liquids derived from L-proline were able to catalyze the reaction. The Michael adduct was obtained in good yield and diastereoisomeric ratio of 19:1 (syn:anti).