A cascade reaction between enaminones, hydrazines, and dimethyl sulfoxide (DMSO) for the synthesis of 1,4-disubstituted pyrazoles catalyzed by molecular iodine in the presence of Selectfluor has been realized. DMSO plays a dual role as the C1 source and the reaction medium. In addition, the synthesis of 1,3,4-trisubstituted pyrazoles using aldehydes as alternative C1 building blocks has also been achieved.

A practical protocol for the synthesis of 4-sulfonyl pyrazoles via the reactions of readily available N,N-dimethyl enaminones and sulfonyl hydrazines has been developed via the catalysis of molecular iodine in the presence of TBHP and NaHCO 3 at room temperature. The pyrazole products have been constructed via the tandem C(sp 2 )À H sulfonylation and a pyrazole annulation without employing any transition metal catalyst or reagent, thus providing a practical new method for the synthesis of the novel pyrazoles bearing a sulfonyl side chain in the heterocycle.

The cleavage on the C=C double bonds of N,Ndimethyl enaminones is initiated by a thermo-induced freeradical transformation, enabling the chemo-selective synthesis of α-acyloxyl ketones. The Mn(II)-assisted single-electron transfer (SET) from the free radical intermediate resulting from addition of the carboxyl radical to enaminone is the key process in modulating the expected reaction pathway.

Abundant pocket-like defects are engineered on the edge of carbon nitride nanodots (CN1.9), using hydrazine groups to attack carbon atoms which results in CN heterocycle opening of porous graphitic C3N4. These edge defects on CN1.9 not only modulate the electronic structure, extend light absorption, and promote photoexcited electron transfer but also lead to c­(HCO3 –)/c­(CO2, aq)-dependent photocatalytic CO evolution in CO2 bubbling HCO3 – aqueous solution (pH ≈ 7.1∼7.5). Even in the N2/HCO3 – system (pH ≈ 8.17), wherein c­(HCO3 –) is about 67 times higher than c­(CO2, aq), the CO production also attains 48.6 μmol g–1 h–1 on CN1.9. In the same experimental condition, almost no CO produces except for H2 on graphitic carbon nitride (GCN). DFT theoretical calculation reveals that edge defects prefer to contact with HCO3 – and proton to orient a special reaction pathway of HCO3* → H2CO3* → CO on CN1.9 with a relatively low-energy barrier rather than HCO3* → H2O–CO2* → CO on GCN.

Defects on metal oxide have attracted extensive attention in photo‐/electrocatalytic CO2 reduction. Herein, porous MgO nanosheets with abundant oxygen vacancies (Vos) and three‐coordinated oxygen atoms (O3c) at corners are reported, which reconstruct into defective MgCO3·3H2O exposing rich surface unsaturated ‐OH groups and vacancies to initiate photocatalytic CO2 reduction to CO and CH4. In consecutive 7‐cycle tests (each run for 6 h) in pure water, CO2 conversion keeps stable. The total production of CH4 and CO attains ≈367 µmol gcata−1 h−1. The selectivity of CH4 gradually increases from ≈3.1% (1st run) to ≈24.5% (4th run) and then remains unchanged under UV‐light irradiation. With triethanolamine (3.3 vol.%) as the sacrificial agent, the total production of CO and CH4 production rapidly increases to ≈28 000 µmol gcata−1 in 2 h reaction. Photoluminescence spectra reveal that Vos induces the formation of donor bands to promote charge carrier seperation. A series of trace spectra and theoretical analysis indicate Mg‐Vo sites in the derived MgCO3·3H2O are active centers, which play a crucial role in modulating CO2 adsorption and triggering photoreduction reactions. These intriguing results on defective alkaline earth oxides as potential photocatalysts in CO2 conversion may spur some exciting and novel findings in this field.