Asymmetric Tandem Michael Addition/Interrupted Nef Reactions of Nitromethane with Oxindole-Derived Alkenes: Enantioselective Synthesis of Spiro-polycyclic Oxindoles.

Chiral spiro-polycyclic oxindoles are valuable heterocyclic ring systems that are widely distributed in natural alkaloids and biologically active compounds. Herein, we reported an asymmetric tandem Michael addition/interrupted Nef reaction of nitromethane with oxindole-derived alkenes catalyzed by a chiral 2-aminobenzimidazole bifunctional organocatalyst. A series of novel enantiomerically enriched spiro-polycyclic oxindole derivatives bearing an oxime group were synthesized in moderate to excellent isolated yields (up to 99%) with an excellent level of enantioselectivities (up to 99% ee). Furthermore, the antiproliferation activity of the resulting oxindoles derivatives were evaluated, and compound 2d demonstrated promising anticancer properties against HCT116 (IC50 = 14.08 µM) and HT29 (IC50 = 15.46 µM) cell lines.

Comparing solution-gate and bottom-gate nanowire field-effect transistors on pH sensing with different salt concentrations and surface modifications.

Field-effect transistors (FETs) have been developed as pH sensors by using various device structures, fabrication technologies, and sensing film materials. Different transistor structures, like extended-gate (EG) FETs, floating-gate FET sensors, and dual-gate (DG) FETs, can enhance the sensor performance. In this article, we report the effects of using solution-gate and bottom-gate FET configurations on pH sensing and investigate the influence of different ionic concentrations of buffers in the measured signals. The surface charge of hafnium dioxide (HfO2) affected by the buffer pH, with/without the modification of polyethylene glycol (PEG) terminated with hydroxyl groups, and the location of applied gate voltage are vital factors to the sensor performance in pH sensing. Based on the results, the solution-gate FET exhibits good pH sensitivity even in the high ionic strength solutions of bis-tris propane (BTP), and these values of pH sensitivity are close to the Nernst limit (59.2 mV/pH). In general, silane-PEG-OH modification can reduce the deviations of measured signals in pH sensing. The performance of bottom-gate FET is inferior in the BTP buffers with high ionic solutions but suitable to be operated in low ionic concentrations, such as 0.1, 1, and 10 mM BTP buffers. The size of the ions was also studied and discussed. The solution-gate FET demonstrates excellent performance under high ionic strengths, meaning a more significant potential for detecting biological molecules under physiological conditions.

Solvent-Controlled Regioselective Reaction of 2-Methyleneaziridines with Acrylic/Propargylic Acids: Synthesis of Carboxylate Aziridine/Acetone Esters.

Herein, we report a convenient solvent-controlled regioselective esterification to access two types of carboxylate esters without any additive or non-green activation strategy. In this transformation, 2-methyleneaziridines served as an ester reagent, providing two alternative electrophilic carbon centers. Notably, this protocol is suitable for some structure-complicated clinical molecules with a carboxylic acid group, presenting remarkable application potential.