Análise da diastereosseletividade da espiro-ciclopropanação de azalactonas promovida por um ilídeo de sulfoxônio

Abstract

Azlactones are five-membered heterocycles characterized by the presence of various chemically active centers, which imparts great versatility regarding the products that can be derived from them; they are particularly important in the pharmaceutical field as precursors to natural and non-natural amino acids. Sulfoxonium ylides are highly reactive chemical species used to form cyclic compounds such as aziridines, epoxides, and cyclopropanes. Accordingly, this project aimed to modify two azlactone structures via spiro- cyclopropanation reaction to investigate the diastereoselectivity and the effect of substituents on the reaction's diastereomeric ratio. The reaction was carried out using two azlactones—(Z)- 4-benzylidene-2-phenyloxazol-5(4H)-one and (Z)-4-(2-furanylidene)-2-phenyloxazol-5(4H)- one—yielding two distinct diastereomers for each; the trans isomer was the major product and represents a novel compound in the literature. Diastereoselectivity was analyzed via 1H nuclear magnetic resonance (NMR) spectroscopy of the crude reaction mixture, revealing diastereomeric ratios of 3:1 for the first compound and 1:1 for the second. The crude reaction mixtures were subjected to column chromatography, allowing for the isolation of only the minor product in the first case and both products in the second. The successfully isolated isomers were characterized by 1H and 13C NMR..