Gold-Catalyzed Formal C-C Bond Insertion Reaction of 2-Aryl-2-diazoesters with 1,3-Diketones

Asymmetric Carbene Transformations for the Construction of All-Carbon Quaternary Centers

Asymmetric catalytic carbene reactions have been well documented in the last few decades for the expeditious assembly of chiral molecules with structural diversity. However, the enantioselective construction of all-carbon quaternary centers remains a challenge in this area. In this review article, two types of asymmetric carbene reactions that beyond cyclopropanation, cyclopropenation, and Büchner reaction, have been summarized for the construction of all-carbon quaternary centers: 1) using carbene species as a 1C synthon that reacts with a trisubstituted prochiral center; 2) sequential installation of two different C-C bonds on the carbene position, which features a gem-difunctionalization reaction. Especially, the asymmetric metal carbene gem-dialkylation process, which has emerged as a practical and versatile method for the expeditious assembly of complex architectures from readily available chemical resources, is a complementary approach for the expeditious assembly of all-carbon quaternary centers.

Dioxane promoted photochemical O-alkylation of 1,3-dicarbonyl compounds beyond carbene insertion into C-H and C-C bonds

A photochemical synthesis of enol ethers and furan-3(2H)-ones from 1,3-dicarbonyl compounds and aryl diazoacetates has been developed. Significantly, 1,4-dioxane promoted O-alkylation of various 1,3-dicarbonyl compounds beyond previous carbene insertion into C-H and C-C bonds has been disclosed.

Uncommon carbene insertion reactions

Transition-metal-catalysed carbene insertion reaction is a straightforward and efficient protocol for the construction of carbon–carbon or carbon–heteroatom bonds. Compared to the intensively studied and well-established “common” carbene insertion reactions, including carbene insertion into C–H, Si–H, N–H, O–H, and S–H bonds, several “uncommon” carbene insertion reactions, including carbene insertion into B–H, Sn–H, Ge–H, P–H, F–H, C–C, and M–M bonds, have been neglected for a long time. However, more and more studies on uncommon carbene insertion reactions have been disclosed recently, and clearly demonstrate the great synthetic potential of these reactions. The current perspective reviews the history and the newest advances of uncommon carbene insertion reactions, discusses their potential applications and challenges, and also presents an outlook of this promising field.

Transition-metal-catalysed carbene insertion reaction is a straightforward and efficient protocol for the construction of carbon–carbon or carbon–heteroatom bonds.

A Selective C-C Bond Cleavage Strategy Promoted by Visible Light

A new visible-light-promoted reaction between aryldiazoacetates and 1,3-diketones allows good yields and selectivities for C-C bond insertions, leading to the corresponding 1,4-dicarbonyl compounds. This transformation is straightforward and highly practical. It tolerates air and moisture and does not require the use of any metals. Mechanistic investigations support the involvement of a key cyclopropanol intermediate derived from an intramolecular rearrangement.

Recent Progress in the Synthesis of Heterocycles Based on 1,3-Diketones

N,O-heterocycles containing the dicarbonyl ring play a significant role in heterocyclic and therapeutic chemistry. Since the discovery of 1,3-diketones, numerous research works have been achieved regarding the synthesis and its chemical reactivity. In this review, we have described the most relevant publications involving β-diketone compounds published during the period between 2018 to date. In addition, we include the 1,3-diketones-based heterocyclic compounds prepared by various synthetic methodologies.

Valence, Size, and Shape Control of Gold Nanoparticles Synthesized by Electron-Assisted Reduction

An electron-assisted strategy was developed to prepare gold nanoparticles (AuNPs) at room temperature. Glow discharge plasma as electron source was successfully used to control the valence state, size, and shape of AuNPs. Stable Au(I) was obtained in 3 min by plasma, and Au(I) was reduced to zero valence with the increase in treatment time. An increase in the amount of Au did not induce an increase in particle size. A narrow size distribution was also achieved. The narrowest size distribution was observed at 9 min at 600 V. AuNPs grew slowly under glow discharge plasma, which slightly changed the mean size of AuNPs. Moreover, the average size of AuNPs was smaller under alkaline conditions. The initial pH of the solution can affect the nucleation and growth of AuNPs and further affect their particle size. Spherical AuNPs, hexagonal AuNPs, rectangular AuNPs, flower-shaped AuNPs, and Au nanorods were easily obtained within 30 min by adding different additives. The hexagonal AuNPs exhibited the largest current response toward caffeine and showed a good linear range (0.1-1000 μM) with a low detection limit (0.064 μM), because their high-energy planes can increase the electron transfer rate and improve electrocatalytic activity.