Reação de Henry catalisada por hidrolases livres e imobilizadas em nanotubos de carbono

Abstract

Among various C-C bond formation reactions, Henry's reaction is widely used in the chemical and pharmaceutical industry, due to the versatility of the β-nitro alcohols formed. However, the broad applicability of these compounds is restricted by the absence of suitable catalysts to impart a defined stereochemistry to the stereogenic centers generated, so the search for catalysts that induce this selectivity is of great interest. Enzymes are catalysts with great potential for this purpose, since they present high selectivity, be it regio, enantio or chemoselective. However, these catalysts may present some disadvantages, such as denaturation at high temperatures or extreme pHs, and that in their free form, they present difficulties in reuse in a new catalytic cycle. To minimize these disadvantages, immobilization techniques are used, where several materials are used as support in the immobilization of enzymes, and the use of carbon nanotubes is the focus of many studies. Therefore, the objective of this work was to evaluate the catalytic efficiency of different commercial hydrolases PPL (porcine pancreatic lipase), Lipozyme 435 (Candida antarctica lipase) and native LIPC12 (metagenomic lipase) and papain in their free or immobilized form in multiple wall carbon nanotubes (MWCNTs) in the synthesis of -nitro-1- (4-nitrophenyl)ethanol, from p-nitrobenzaldehyde and nitromethane and compare their results using a standard organocatalyst, L-proline. The obtained products were characterized and quantified by 1H NMR and FT-IR. Conversions to 2-nitro-1-(4-nitrophenyl)ethanol were 69-80% using the enzymes in their free form, and this result was similar to that obtained using L-proline (74%). PPL enzyme was chosen for having greater conversion. Another study showed the influence of the solvent used in the reaction, when using solvents of different hydrophobicities such as DMSO, water, cyclohexane and the eutectic solvent formed by choline chloride/urea 1: 2 (DES), the product of the reaction was obtained with conversion rates of 35 to 99% in 48h, where the DES presented significant results, with conversions above 99%, so in another study the use of these solvents was evaluated in lower times, with or without addition of water, and conversions to the respective product ranged from 34 to 99% in 24 hours. After optimization of the reaction conditions the effect of the immobilized was evaluated using PPL / MWCNTs and LIPC12 / MWCNTs in the synthesis of β-nitroalcohol. In this the conversions to the product were larger using the fixed asset, in particular the LIPC12, with increase of 23%.