Practical chemoselective aromatic substitution: the synthesis of -(4-halo-2-nitrophenyl)benzenesulfonamide through the efficient nitration and halogenation of -phenylbenzenesulfonamide.

A novel route involving the metal-promoted tandem nitration and halogenation of -phenylbenzenesulfonamide to synthesize -(4-halo-2-nitrophenyl)benzenesulfonamide derivatives has been developed. The method shows highly practical chemoselective and functional group compatibility. In addition, it employs insensitive and inexpensive Cu(NO)·3HO, Fe(NO)·9HO, and NHNO as the nitration reagents, and it provides a direct approach for the preparation of 4-halo-2-nitroaniline, which is a crucial intermediate for the synthesis of benzimidazoles and quinoxaline derivatives.

Rhodium-Catalyzed Regioselective Formal Hydroacylation of Vinyl Epoxides toward Esters Involving β-Carbon Cleavage.

Herein we disclose the first example of the formal hydroacylation reactions of vinyl epoxides with chelating aldehydes enabled by rhodium catalysis for the efficient construction of functionalized esters. Detailed investigations of the mechanistic pathway reveal that the presence of a 2-vinyl group is essential in contributing to the success of this regioselective reaction, which might proceed through β-carbon cleavage as the key procedure.

Upconversion nanoparticles for ratiometric fluorescence detection of nitrite.

We have developed a selective upconversion switching method for the ratiometric fluorescence detection of nitrite using upconversion nanoparticles (UCNPs) and an efficient nitrite reaction. The green emission (λ(em) = 539 nm) of NaYF4:Yb(3+),Er(3+) nanoparticles can be selectively quenched by the neutral red (NR) dye due to the spectral overlap between the emission at 539 nm and the absorption of NR, while its red emission (λ(em) = 654 nm) remains unchanged. Nitrite reacts specifically and strongly with NR to form diazonium salt and lose the diazonium group, which sharply decreases the absorption of NR.

An efficient synthesis of 3,4-dihydropyrimidin-2-ones catalyzed by NH2SO3H under ultrasound irradiation.

The condensation of aldehydes, beta-keto esters and urea catalyzed by NH(2)SO(3)H in ethanol results dihydropyrimidinones in high yields under ultrasound irradiation.