Efficient synthesis and antitumor evaluation of 4-aminomethyl-N-arylpyrazoles: Discovery of potent and selective agents for ovarian cancer

A new one-pot two-step sequential methodology for synthesis of novel 3-carboxyethyl 4-[(tert-butylamino)methyl]-N-arylpyrazole derivatives is reported. One-pot transformation of β-enamino diketones and arylhydrazines generated 4-iminium-N-arylpyrazole salt intermediates in situ, which were easily transformed into 4-[(tert-butylamino)methyl]-N-arylpyrazole derivatives by NaBH₃CN. The products could be isolated in the free or hydrochloride salt forms. Also, it was possible to obtain the products in the zwitterionic form by ester group hydrolysis. Furthermore, all synthesised compounds were evaluated in vitro against a panel of eight human tumor cell lines. The 4-[(tert-butylamino)methyl]-N-arylpyrazole derivatives were much more powerful than the hydrochloride and zwitterionic forms. Moreover, the results suggest that the N-aryl group at the pyrazole ring is vital for modulating antiproliferative activity. The 3-carboxyethyl 4-[(tert-butylamino)methyl]-N-phenylpyrazoles 3a-g exhibited higher inhibitory activities against OVCAR-3, with GI₅₀ values of 0.013-8.78 μM, and lower inhibitory activities against normal human cell lines. Molecular docking was performed to evaluate the probable binding mode of 3a into active site of CDK2.

One-pot synthesis and radical scavenging activity of novel polyhydroxylated 3-arylcoumarins

An unexpected domino rearrangement brought about the development of a novel one-pot procedure for synthesis of coumarins. This protocol allowed the gram-scale synthesis of a variety of polyhydroxylated derivatives 3a-p, from readily available starting materials at a low cost. Based on two proven intermediates, a probable mechanism consisting of boron tribromide induced demethylation/lactone ring opening/elimination/isomerization/lactone ring closure reaction sequence of in situ formed 3-aryl-3,4-dihydroisocoumarin-4-carboxylic acids was deduced. Compared to the common methods, used for the synthesis of coumarins, the proposed herein possesses great advantages, such as mild conditions, good yields for short reaction time, simple work-up procedure and easy isolation of the final products. The structure of the newly synthesized compounds 3a-p was established by spectroscopic methods ((1)H NMR, (13)C NMR, IR, MS and HRMS) and their radical scavenging activity was evaluated in vitro against 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH). The results obtained show that compounds 3g-p posses higher radical scavenging activity (3.16 ≤ SC50 [μM] ≤ 6.82) than well-known antioxidants such as trolox, protocatechuic acid, caffeic acid and gallic acid (SC50 [μM] = 9.34, 8.83, 9.48, 5.33, respectively), which is a precondition for promising antioxidant activity of these compounds to be expected.

Iridium-catalyzed borylation of thiophenes: versatile, synthetic elaboration founded on selective C-H functionalization

Iridium-catalyzed borylation has been applied to various substituted thiophenes to synthesize poly-functionalized thiophenes in good to excellent yields. Apart from common functionalities compatible with iridium-catalyzed borylations, additional functional group tolerance to acyl (COMe), and trimethylsilyl (TMS) groups was also observed. High regioselectivities were observed in borylation of 3-and 2,5-di-substituted thiophenes. Electrophilic aromatic C-H/C-Si bromination on thiophene boronate esters is shown to take place without breaking the C-B bond, and one-pot C-H borylation/Suzuki-Miyaura cross-coupling has been accomplished on 2- and 3-borylated thiophenes.