PhICl2-Mediated Regioselective and Electrophilic Oxythio/Selenocyanation of o-(1-Alkynyl)benzoates: Access to Biologically Active S/SeCN-Containing Isocoumarins.

The application of PhICl2/NH4SCN and PhICl2/KSeCN reagent systems to the synthesis of the biologically active S/SeCN-containing isocoumarins via a process involving thio/selenocyanation, enabled by thio/selenocyanogen chloride generated in situ, followed with an intramolecular lactonization was realized. Gram-scale synthesis, further derivatization to access C4 thio/selenocyanated Xyridin A and anti-tumor activities of the obtained products highlight the potential use of this method.

Construction of the 2-Amino-1,3-selenazole Skeleton via PhICl2/KSeCN-Mediated Selenocyanation/Cyclization.

The construction of 2-amino-1,3-selenazole skeleton was realized via the PhICl2/KSeCN-enabled electrophilic selenocyanation of ß-enaminones and ß-enamino esters followed by intramolecular cyclization under basic conditions. Compared to the classical Hantzsch strategy that utilizes selenourea or its analogues as starting materials or crucial intermediates, this method might represent an alternative approach for the assembly of 1,3-selenazole framework through a different pathway.

Construction of 2-Arylbenzo[4,5]thieno[2,3-d]thiazole Skeleton via CuCl/S-Mediated Three-Component Reaction.

An exclusive thiophene-fused polycyclic π-conjugated 2-arylbenzo[4,5]thieno[2,3-d]thiazole skeleton was constructed via a one-pot CuCl-mediated three-component reaction, using 2-(2-bromophenyl)acetonitrile and aromatic aldehydes as substrates and elemental sulfur as sulfur source in the presence of K2CO3 and 1,10-phen in DMSO. A plausible reaction mechanism was proposed, which involved formation of benzo[b]thiophen-2-amines through cyclization of 2-bromophenyl acetonitrile and sulfur, and subsequent intramolecular condensation/dehydrogenation with aromatic aldehydes.

Synthesis and Characterization of the Perthiatriarylmethyl Radical and Its Dendritic Derivatives with High Sensitivity and Selectivity to Superoxide Radical.

EPR spectroscopy, coupled with the use of tetrathiatriarylmethyl (TAM) radicals, has been a reliable method to detect the superoxide radical (O2.- ). However, the specificity and biocompatibility of TAM radicals need to be further improved. Although derivatization may overcome the drawbacks of current TAM radicals, esterification or amidation through the carboxylic groups greatly changes their redox properties and makes them inert to O2.- . Herein, the synthesis of a perthiatriarylmethyl (PST) radical and its dendritic derivatives, PST-TA and PST-NA, in which PST is covalently linked with dendrons containing three (TA) and nine (NA) carboxylic acids, respectively. The results show that PST rapidly reacts with O2.- to yield a unique quinone methide product. Dendritic modification of PST slightly decreases the reactivities of PST-TA and PST-NA, but notably increases their biostability toward various oxidoreductants. The detection limit of PST-NA to O2.- was estimated to be 2.1 nm min-1 over 60 min of detection. Importantly, PST-NA shows threefold higher sensitivity to O2.- in the presence and absence of ascorbic acid than that of the classic spin-trapping technique. In addition, the application of PST-NA to detect extracellular O2.- generation in stimulated RAW 264.7 macrophages was also explored. This study demonstrates that PST-NA has great potential for specific detection and quantitation of O2.- in extracellular sites.