NOVEL REDUCTION OF ARYL NITRO GROUPS ON HETEROCYCLES USING CACL2, FE, AND GLACIAL ACETIC ACID
Jorge Becerra, George R. Negrete.
The University of Texas at San Antonio, San Antonio, TX.
Reductions of nitro groups on aromatic compounds are important when applied to organic molecules aimed at biological systems. These reductions are not only expensive and time consuming to produce, but require harmful materials such as lithium aluminum hydride, sodium borohydride, or palladium. To avoid using these reagents and reaction conditions, a new method was reported by Rangappa et al., for reducing the nitro group on aromatic rings using CaCl2, Fe, H2O, and ethanol. The main emphasis of our laboratory has been synthesizing novel cysteine-derived lipid analogs (CLAs) as potential antibiotics that can be armed with a peptide sequence that induces apoptosis. The heterocycle contains a thiazolidine core with an acryloyl group that can be coupled with alkyl or aryl thiols via conjugate addition and carboxylic acid and aryl nitro groups. The latter can be reduced to an amine (Pd/hydrogen) such that the carboxyl and amino groups can be employed to append a peptide chain and a fluorophore via peptide coupling methods. The aryl nitro group reduction was investigated using a CLA bearing a benzylthio ether unit. Initial reactions following the method of Rangappa showed no product formation according to 1H NMR data, but more vigorous conditions gave samples exhibiting 1H NMR signals that were shifted up-field compared to the aryl nitro group signals along with other signals expected for the desired product. The result for these studies will be presented.