Organic Chemistry Frontiers最新文献

A chemo- and regioselective synthesis of 2-benzhydryl and 2,3-disubstituted indoles via cyclization and regiocontrolled Truce–Smiles (T–S) rearrangement is disclosed. A cascade 5-endo-dig cyclization of 2-amino diphenylacetylenes mediated by KN(SiMe₃)₂ is followed by a regiocontrolled T–S reaction. This system provides the first example of T–S regioselectivity and is controlled by ligands on K⁺.

Facilitated by electron donor–acceptor complexes, an efficient dehydrogenative β-trifluoromethylthiolation of tertiary amines with N-trifluoromethylthiophthalimide is presented under transition-metal-free, external oxidant-free, photocatalyst-free and mild reaction conditions. This protocol accommodates a range of substituted piperidines, as well as seven- and eight-membered saturated heterocycles. Additionally, employing this photocatalyst-free approach, direct β-trifluoromethylthiolation of electron-rich enamides was also achieved through the involvement of a photoactive electron donor–acceptor (EDA) complex.

Direct coupling of inert C–H bonds by N-heterocyclic carbenes (NHCs) represents a fascinating area of research in organocatalysis. Recently, several notable studies have disclosed the potential of NHCs to directly functionalize latent C–H bonds of diverse simple molecules (e.g., ethers, amines, and arenes). These methodologies offer straightforward and efficient routes for C–C bond-forming transformations by diminishing the need for prefunctionalization manipulations of inert C–H bonds, allowing for the synthesis of a broad range of high value-added functional ketone molecules. Consequently, this highlight aims to present the latest advancements in NHC organocatalysis, specifically focusing on direct coupling functionalization of inert C–H bonds involving the electron or proton transfer process (ET/PT pathways) and hydrogen atom transfer pathway (HAT pathway).

An efficient palladium-catalyzed post-Ugi dearomative cyclization has been achieved, enabling the rapid assembly of diverse benzoazepinespiroindolenine derivatives with excellent chemoselectivity and good diastereoselectivity. This methodology can controllably introduce functionality and complexity into the dearomatized alicyclic products in a cost-effective and step-economical manner with a wide range of substrate scope. The highly precise dearomatization of complex Ugi adducts opens the door to address formidable chemoselectivity issues among nucleophilic sites, and complements the functional group compatibility of the classical dearomatization protocols. Density functional theory (DFT) calculations shed light on the reaction mechanism as well as the origin of chemoselectivity.

A novel phosphine-catalyzed asymmetric aza-Morita–Baylis–Hillman reaction of endocyclic ketimines with vinyl ketone or acrolein has been presented. This approach resulted in densely functionalized adducts with moderate to high yields and enantioselectivities (up to 97% yield, up to 97% ee), with the feature of a C2 tetra-substituted chiral center on a 3-oxindole scaffold. A wide variety of substrates were compatible with this methodology, and diverse enantiomeric products could be obtained through a catalyst switching strategy. A series of transformations further demonstrated the utility of this methodology.

An unprecedented electrochemically regioselective C–H phosphorothiolation and S- to C-[1,4] phosphoryl migration involving indolizines, elemental sulfur, and H-phosphonates in an undivided cell has been developed. This strategy utilizes elemental sulfur as an odorless sulfur source, providing a new avenue for the formation of C(sp²)–S–P bonds under sustainable conditions. Various phosphorothiolated and mercapto-phosphono substituted indolizines were obtained via controllable electrochemical phosphorothiolation and a 1,4-S → C phospho-Fries rearrangement. Additionally, this is the first example of successive electrochemical phosphorothiolation and a 1,4-S → C phospho-Fries rearrangement.