A selective and high yielding synthesis of polysubstituted pyrazoles through a VLPC (visible light photoredox catalysis)-promoted reaction of hydrazine with Michael acceptors is reported. The method employs very mild reaction conditions and uses air as the terminal oxidant, which makes the process environmentally benign. Different types of Michael acceptors with various substituents can undergo the reaction to afford corresponding pyrazoles in good to excellent yields. The reaction is proposed to go through VLPC-promoted oxidation of hydrazine to diazene followed by its addition to Michael acceptors, other than the conventional condensation of hydrazine with a carbonyl.

A metal-free protocol through visible light mediated oxidative cleavage of CC bonds to directly construct CN bonds has been developed for the conversion of alkenes to hydrazones under mild conditions.

Over the past few decades, ylide chemistry has been significantly extended to an area beyond olefination and small ring formation, among which ylide [4 + 1] annulation has been extensively explored, and five-membered ring structures, such as dihydrofurans, isoxazolines, pyrrolines, indoles, dihydropyrazoles and cyclopentenones, can be readily constructed through this type of transformation. An overview of the recent advances in this field is presented herein. Ylide [4 + 1] annulations are reviewed by highlighting their product diversity, selectivity and applicability, and the mechanistic rationale is presented when possible.

A green and cost-effective method has been developed for the conversion of alkenes to ketones under metal-free conditions.

1-Ethyl-3-methylimidazolium chlorine ([Emim]­Cl) and 1-ethyl-3-methylimidazolium bromide ([Emim]­Br) as an additive to working fluid [lithium bromide aqueous solution (H2O/LiBr) and lithium chloride aqueous solution (H2O/LiCl)] of absorption cycles were proposed. The vapor pressure of H2O + LiCl + [Emim]Cl (mass ratio LiCl/[Emim]Cl = 2) in the temperature from 314.79 to 435.48 K, H2O + LiCl + [Emim]Br (mass ratio LiCl/[Emim]Br = 2) in the temperature from 317.62 to 431.27 K, and H2O + LiBr + [Emim]­Cl (mass ratio LiBr/[Emim]Cl = 2) in the temperature from 303.10 to 409.91 K was measured by the boiling point method. The mass fractions of the absorbent were from 0.30 to 0.60. The experimental data were regressed using the Antoine-type equation, and the average absolute relative deviation (AARD %) between the experimental data and calculated values of three systems was 0.44, 0.51, and 0.54%. Compared with that of the previously reported ionic liquids, ([Emim]­Ac) as an absorbent for LiBr + H2O, vapor pressure of these four systems follows the order LiCl + [Emim]Cl + H2O < LiCl + [Emim]Br + H2O < LiBr + [Emim]Cl + H2O < LiBr + [Emim]­Ac + H2O. The proposed ternary systems have better water affinity and can be promising alternative working fluids in the absorption cooling system.