Brønsted Acid-Catalyzed Minisci-Type Cross-Dehydrogenative Coupling of N-Heteroaromatics and Cyclic Ethers

Minisci Reaction by an MW-Boost: A Simple Protocol for Site-Selective Dehydrogenative Cross-Coupling Between Nitrogen-Aromatics and C(sp3)─H Bonds

The Minisci-type reaction between C(sp3)─H bonds and nitrogen-containing aromatics was carried out using a simple protocol based on the persulfate anion (PS) under microwave (MW) irradiation. The MW/PS protocol is applicable to a wide variety of dehydrogenative coupling reactions of N-heteroaromatics and C(sp3)─H bonds, leading to the formation of alkylated heteroaromatics. Site-selectivity is ensured by hydrogen atom transfer (HAT) with the sulfate radical affecting the polar/steric effects in the transition state. The MW/PS protocol was applicable to direct intramolecular cyclization to give five and six-membered rings fused by pyridine and lutidine, which, in previous methods, it was necessary to use tedious derivatization to imino-oxyacetic acids as HAT precursors.

Synthesis of naphthalene derivatives via nitrogen-to-carbon transmutation of isoquinolines

Heteroarene skeletal editing is gaining popularity in synthetic chemistry. Transmuting single atoms generates molecules that have distinctly varied properties, thereby fostering potent molecular exchanges that can be extensively used to synthesize functional molecules. Herein, we present a convenient protocol for nitrogen-carbon single-atom transmutations in isoquinolines, which is inspired by the Wittig reaction and enables easy access to substituted naphthalene derivatives. The reaction uses an inexpensive and commercially available phosphonium ylide as the carbon source to furnish a wide range of substituted naphthalenes. The key to the success of this transformation is the formation of a triene intermediate through ring opening, which undergoes 6π-electrocyclization and elimination processes to afford the naphthalene product. Furthermore, this strategy enables the facile synthesis of 13C-labeled naphthalenes using 13CH3PPh3I as a commercial 13C source and facilitates modifying the directing group for C─H functionalization.

Ag-Catalyzed cross-dehydrogenative-coupling for the synthesis of 1,4-dioxan-2-yl substituted quinazoline hybrids in an aqueous medium

We herein developed an effective approach for the construction of 2- or 4-(1,4-dioxan-2-yl) substituted quinazolines under mild conditions. A silver-K2S2O8 catalyzed direct CDC reaction between quinazolines and 1,4-dioxane for the synthesis of a series of 2- or 4-(1,4-dioxan-2-yl) substituted quinazoline hybrids is reported. The reaction proceeded well in water under mild conditions and showed a broad substrate scope and good functional group compatibility.

Minisci-Type Dehydrogenative Coupling of N-Heteroaromatic Rings with Inert C(sp3)-H Enabled by a Visible-Light-Catalyzed Intermolecular Hydrogen Atom Transfer Process

The Minisci-type dehydrogenative coupling of N-heteroaromatic rings with inert C-H or Si-H partners via visible-light-catalyzed hydrogen atom transfer has been reported. This methodology allows the coupling reactions to be carried out in water as a solvent under air atmospheric conditions with visible-light illumination. A wide range of inert C-H and Si-H partners could be directly coupled with various N-aromatic heterocycles to deliver products in good to excellent yields.

Phototriggered Self-Catalyzed Three-Component Minisci Reaction: A Route to β-C(sp3) Heteroarylated Alcohols/Ethers

Herein, a visible-light-triggered photocatalyst-free radical cascade Minisci reaction of heteroarenes, alkenes, and water/alcohols to obtain diverse β-C(sp³) heteroarylated alcohols/ethers has been developed. Achieved under mild and simple conditions, this protocol is scalable and features broad substrate scope and functional group tolerance. Mechanistic studies demonstrate that the heteroarene can be served as a photocatalyst to engage single-electron transfer with persulfate.

Scaffold hopping by net photochemical carbon deletion of azaarenes

Discovery chemists routinely identify purpose-tailored molecules through an iterative structural optimization approach, but the preparation of each successive candidate in a compound series can rarely be conducted in a manner matching their thought process. This is because many of the necessary chemical transformations required to modify compound cores in a straightforward fashion are not applicable in complex contexts. We report a method that addresses one facet of this problem by allowing chemists to hop directly between chemically distinct heteroaromatic scaffolds. Specifically, we show that selective photolysis of quinoline N-oxides with 390-nanometer light followed by acid-promoted rearrangement affords N-acylindoles while showing broad compatibility with medicinally relevant functionality. Applications to late-stage skeletal modification of compounds of pharmaceutical interest and more complex transformations involving serial single-atom changes are demonstrated.

CF3SO2Na-Mediated Visible-Light-Induced Cross-Dehydrogenative Coupling of Heteroarenes with Aliphatic C(sp3)-H Bonds

Minisci-type reaction is one of the important means to construct C(sp³)-H functionalization of heteroarenes. According to traditional methods, stoichiometric amounts of precious transition metal catalysts and chemical oxidants were required at high temperatures. Here, a green and gentle novel Minisci-type method was developed via visible-light-induced cross-dehydrogenative coupling of heteroarenes with aliphatic C(sp³)-H bonds under oxidant-free and transition-metal-catalyst-free conditions. Only the catalytic equivalent of CF₃SO₂Na and room temperature were required to maintain an efficient reaction.