Photoredox cross-dehydrogenative C(sp2)-C(sp3) coupling of heteroarenes with secondary amines through 1,5-HAT.

The functionalization of α-C(sp3)-H bonds in amines has become a focal point of contemporary research. Here, we report a new approach utilizing photocatalysis α-C(sp3)-H bond functionalization in alicyclic and aliphatic secondary amines facilitated by intramolecular 1,5-hydrogen atom transfer (HAT). This finding unlocks a sustainable method for rapidly constructing complex heterocyclics via cross-dehydrogenative C-C coupling of protected amines and nitrogen-containing heterocycles. This protocol boasts broad applicability to various substrates, exhibits tolerance to numerous functional groups, and supports the late-stage modification of drug molecules.

Catalytic C(sp3)-H Trifluoroethylation of Amino Acids and Carboxylic Acids.

Integrating of the trifluoroethyl (-CH2CF3) group into the organic compounds by activating the distal C(sp3)-H bond is a challenging but crucial task in organic chemistry. This transformation imparts unique physicochemical properties to the compounds, such as enhanced lipophilicity, metabolic stability, and altered electronic characteristics. In this study, we unveil a new palladium-catalyzed method to directly introduce the trifluoroethyl group into amino acid and carboxylic acid derivatives. Remarkably, this method effectively activates the ß-C(sp3)-H bond across various substrates at room temperature. Utilizing mesityl(2,2,2-trifluoroethyl)iodonium triflate as a trifluoroethyl source, our approach selectively targets the distal ß-C(sp3)-H bonds of amino and carboxylic acids, ensuring high chemoselectivity and enabling the straightforward synthesis of a diverse array of important γ-trifluoromethyl amino acid and carboxylic acid derivatives. Furthermore, the practical applicability of this methodology is demonstrated through its scalability for gram-scale synthesis.

Visible light-induced organo-photocatalyzed route to synthesize substituted pyrazoles.

The synthesis of tetra-substituted pyrazoles holds significant synthetic value and has been accomplished through an organo-photocatalyzed decarboxylative intramolecular cyclization using readily available 1,2-diaza-1,3-dienes and α-ketoacids. This method allows for the systematic synthesis of substituted pyrazole derivatives. Notably, this approach is characterized by its metal-free and oxidant-free nature, offering distinct advantages such as short reaction times and exceptionally mild reaction conditions. The developed methodology enables the efficient construction of tetra-substituted pyrazoles, expanding the available chemical space for exploration and opening up potential applications in various scientific fields.

Organophotocatalyzed Alkyl/Arylsulfonylation of Vinylcyclopropanes.

Allyl sulfones are an essential pharmacophore in many bioactive compounds. To combat their synthetic barrier, we report a practical, straightforward organophotocatalyzed methodology for accessing miscellaneously functionalized allyl sulfone derivatives using inexpensive and bench-stable sodium sulfinate salts under mild conditions. This photo-catalyzed radical sulfonylation provides access to a variety of allyl sulfones in good to excellent yields with high E : Z selectivity. A wide range of vinyl cyclopropanes, as well as aryl/hetero and alkyl sodium sulfinates, were tolerated and reliable in gram-scale synthesis. Later on, further functionalization of allyl sulfones was demonstrated. A plausible mechanism for radical sulfonylation is proposed from the control experiments.

Metal and catalyst-free strategy to access 1,3-thio-heteroaryl BCP derivatives.

The widespread presence of bicyclo[1.1.1]pentane (BCP) and sulfur motifs in pharmaceutical compounds underscores the significance of synthesizing suitably functionalized BCP thioethers. In response, we have developed a metal-free and photocatalyst-free strategy that harnesses visible light-induced radical cascades. This approach culminates in the synthesis of essential thio-BCP derivatives, which serve as crucial precursors for the formation of the corresponding sulfoxides, sulfones, and sulfoximines. Importantly, this methodology exhibits potential for large-scale applications, displaying commendable tolerance towards various functional groups while operating under mild reaction conditions.

Metal-Free Photoredox Four-Component Strategy to 1,3-Functionalized BCP Derivatives.

Trifluoromethyl bicyclo[1.1.1]pentanes (BCPs) have attracted significant attention from the scientific community and pharmaceutical industries due to their advantageous physicochemical properties as arene bioisosteres. Initial photoredox perfluoroalkylation of [1.1.1]propellane triggers the tandem reaction to the perfluoroalkyl BCP radical followed by Giese addition to an in situ generated electron-deficient alkene by Knoevenagel condensation in a four-component fashion to form 1,3-functionalized BCPs. This strategy provides easy access to various 1,3-functionalized perfluoroalkyl BCP derivatives with the added advantage of nitrile group as a functional handle to diversified transformations. This methodology offers scalability and late-stage derivatization of drug molecules with high chemoselectivity.

Photoinduced Cascade Difluoroalkylative Ring-Opening of Vinyl Cyclopropanes.

Here, we report a facile and efficient method for the difluoroalkylation of vinyl cyclopropanes (VCPs) using visible-light organophotoredox catalysis. This strategy exploits the interplay of α-amino alkyl radical-mediated halogen-atom transfer (XAT) reaction. The broad substrate scope, excellent functional group compatibility, operational simplicity, inexpensive CF2 precursors, and high efficiency make this protocol promising for the cost-efficient synthesis of allylic difluoroalkylated derivatives.