Visible-Light-Induced Radical Sulfonylative-Cyclization Cascade of 1,6-Enynol Derivatives with Sulfinic Acids: A Sustainable Approach for the Synthesis of 2,3-Disubstituted Benzoheteroles

Benzoheteroles are promising structural scaffolds in the realm of medicinal chemistry, but sustainable synthesis of 2,3-difunctionalized benzoheterole derivatives is still in high demand. Indeed, we have conceptually rationalized the intrinsic reactivity of propargylic-enyne systems for the flexible construction of 2,3-disubstituted benzoheteroles through radical sulfonylative-cyclization cascade under organophotoredox catalysis. We hereby report an efficient visible-light-induced sulfonyl radical-triggered cyclization of 1,6-enynols with sulfinic acids under the dual catalytic influence of 4CzIPN and NiBr2⋅DME, which led to the formation of 2,3-disubstituted benzoheteroles in good to high yields. Additionally, the Rose Bengal (RB)-catalyzed radical sulfonylative-cycloannulation of acetyl-derived 1,6-enynols with sulfinic acids under blue LED irradiation allowed to access 3-(E-styryl)-derived benzofurans and benzothiophenes in moderate to good yields. The scope and limitations of the present strategies were successfully established using different classes of 1,6-enynols and sulfinic acids bearing various sensitive functional groups, yielding the desired products in a highly stereoselective fashion. Plausible mechanistic pathways were also proposed based on the current experimental and control experiments.

Development of a General and Selective Nanostructured Cobalt Catalyst for the Hydrogenation of Benzofurans, Indoles and Benzothiophenes

The selective hydrogenation of benzofurans in the presence of a heterogeneous non-noble metal catalyst is reported. The developed optimal catalytic material consists of cobalt-cobalt oxide core-shell nanoparticles supported on silica, which has been prepared by the immobilization and pyrolysis of cobalt-DABCO-citric acid complex on silica under argon at 800 °C. This novel catalyst allows for the selective hydrogenation of simple and functionalized benzofurans to 2,3-dihydrobenzofurans as well as related heterocycles. The versatility of the reported protocol is showcased by the reduction of selected drugs and deuteration of heterocycles. Further, the stability, recycling, and reusability of the Co-nanocatalyst are demonstrated.

Discovery of novel 5-methoxybenzothiophene hydrazides as metabolically stable Clk1 inhibitors with high potency and unprecedented Clk1 isoenzyme selectivity

Clk1 kinase is a key modulator of the pre-mRNA alternative splicing machinery which has been proposed as a promising target for treatment of various tumour types, Duchenne's muscular dystrophy and viral infections such as HIV-1 and influenza. Most reported Clk1 inhibitors showed significant co-inhibition of Clk2 and Clk4 in particular, which limits their usefulness for deciphering the individual roles of the Clk1 isoform in physiology and disease. Herein, we present a new 5-methoxybenzothiophene scaffold, enabling for the first time selective inhibition of Clk1 even among the isoenzymes. The 3,5-difluorophenyl and 3,5-dichlorophenyl derivatives 26a and 27a (Clk1 IC₅₀ = 1.4 and 1.7 nM, respectively) showed unprecedented selectivity factors of 15 and 8 over Clk4, and selectivity factors of 535 and 84 over Clk2. Furthermore, 26a and 27a exhibited good growth inhibitory activity in T24 cancer cells and long metabolic half-lives of almost 1 and 6.4 h, respectively. The overall favorable profile of our new Clk1 inhibitors suggests that they may be used in in vivo disease models or as probes to unravel the physiological or pathogenic roles of the Clk1 isoenzyme.