Scheme 1Īddition of compound 4 to the aqueous solutions of different anions changed the color of the solution containing cyanide ( Figure 1). All the six phenolic units are directed outward from the central hydrophobic core ( Chart 2). The energy-minimized geometry of compound 4 indicates circular shape of the molecule with the six 3-(4-hydroxy-3,5-dimethoxybenzylidene)indolin-2-one units projecting alternatively upward and downward of the benzene plane. Selective demethylation of compound 9 was achieved by using AlCl 3 in dichloromethane (DCM) providing desired compound 4 ( Scheme 1). Further reaction of compounds 6 and 8 in acetonitrile (ACN) in the presence of K 2CO 3 resulted into the replacement of all the six Br of compound 8 with compound 6, and consequently, compound 9 was procured. For the synthesis of compound 8, first mesitylene was treated with formaldehyde and HBr–AcOH to get compound 7 and then compound 7 was refluxed with Br 2 in 1,2-dibromoethane wherein compound 8 was obtained. Compound 6 was procured as inseparable E- and Z-isomers in the ratio 4:1. Chart 1Ĭompound 5 was obtained by the methylation of syringaldehyde, and it was made to react with oxindole by heating at 145 ☌ to obtain compound 6 ( Scheme 1).
Therefore, it was planned to introduce six 3-(4-hydroxy-3,5-dimethoxybenzylidene)indolin-2-one units on the benzene core, and consequently, compound 4 ( Chart 2) was designed. Hence, it was logically hypothesized that the presence of more such phenolic groups in the molecule may increase its cyanide-sensing capacity and that the capturing of cyanide per molecule of the receptor becomes more effective. (7,8) In addition to the available reports on cyanide sensing (9−18) and sequestering compounds such as hydroxocobalamin, (19−24) dicyanocobalt(III) porphyrins, (25−28) vitamin B12 analogues, (29,30) and hexahydrated dichlorides of cobalt(II), (31−34) it was found recently that compounds 1–3 ( Chart 1) were capable of removing cyanide from the aqueous medium and human blood serum (35,36) through the more prevalent keto-form of their phenolic moiety and disposing it off in the form of COOH. The affinity of CN – for Fe 2+ of cytochrome c (Cyt c) makes it one of the highly toxic anions (1−6) because Cyt c–CcOX (cytochrome c oxidase) complex is the last enzyme in the respiratory electron transport chain and the blockage of this pathway limits the oxygen supply that ultimately proves lethal.