Search

Multi-substituted conjugated dienes are useful intermediates for the synthesis of various biologically active compounds and functional materials. In this study, one-pot synthesis of multi-substituted 2,4-butadienes was achieved via the reaction of ketene dithioacetal, 3,3-bis(methylsulfanyl)methylenemalononitrile (1), with a variety of aromatic ketone compounds. Complete stereoselective (2Z,4E)-2,4-dienamide (3a) was obtained from 1 with 4-methoxyacetophenone (2a) in the presence of sodium hydroxide as a base in DMSO. Similarly, the reaction of 1 with electron-rich aromatic ketones or heterocyclic aromatic ketones gave (2Z,4E)-2,4-dienamide compounds as the sole product in 31–61 yields. In the proposed synthetic sequence, the process consists of a cascade reaction involving the addition of 1 to ketone compound, elimination of methylthiolate anion from 1, subsequent intramolecular cyclization and ring opening reaction by readdition of methylthiolate anion. Moreover, all the (2Z,4E)-2,4-dienamide compounds (3a–j) obtained in this study exhibited blue-green fluorescence in the solid state, which suggested the possibility of obtaining functional conjugated dienes by this novel one-pot synthetic method. [ABSTRACT FROM AUTHOR]

Fluorescence probes that selectively image cadmium are useful for detecting and tracking the amount of Cd2+ in cells and tissues. In this study, we designed and synthesized a novel Cd2+ fluorescence probe based on the pyridine-pyrimidine structure, 4-(methylsulfanyl)-6-(pyridin-2-yl)pyrimidin-2-amine (3), as a low-molecular-weight fluorescence probe for Cd2+. Compound 3 could successfully discriminate between Cd2+ and Zn2+ and exhibited a highly selective turn-on response toward Cd2+ over biologically related metal ions. The dissociation constant (Kd) and the limit of detection (LOD) of 5.4 × 10− 6 mol L− 1 and 4.4 × 10− 7 mol L− 1, respectively, were calculated using fluorescence titration experiments. Studies with closely related analogs showed that the bis-heterocyclic moiety of 3 acted as both a coordination site for Cd2+ and a fluorophore. Further, the methylsulfanyl group of compound 3 is essential for achieving selective and sensitive Cd2+ detection. Fluorescence microscopy studies using living cells revealed that the cell membrane permeability of compound 3 is sufficient to detect intracellular Cd2+. These results indicate that novel bis-heterocyclic molecule 3 has considerable potential as a fluorescence probe for Cd2+ in biological applications. [ABSTRACT FROM AUTHOR]

The original version of this article unfortunately contained a mistake. The equation under "Experimental -- Spectroscopic Studies" section should be corrected as per the following. [ABSTRACT FROM AUTHOR]