Visible-Light-Driven Halogen-Bond-Assisted Direct Synthesis of Heteroaryl Thioethers Using Transition-Metal-Free One-Pot C–I Bond Formation/C–S Cross-Coupling Reaction

Abstract

An efficient protocol for the synthesis of thioether directly from heteroarenes has been developed in the presence of visible light in a one-pot manner at room temperature. This method involves two sequential reactions in a single pot where the formation of the iodinated heteroarene is followed by a transition-metal-free C–S coupling reaction. A wide range of heteroarene and thiol partners (including aliphatic thiols) have been used for the synthesis of thioethers. NMR studies and DFT calculations revealed the presence of a halogen bond between the thiolate anion (halogen bond acceptor) and iodoheteroarene (halogen bond donor). This halogen bonded complex on photoexcitation facilitates the electron transfer from the thiolate anion to the iodoheteroarene at room temperature.

Palladium-Catalyzed Direct C2-Biarylation of Indoles

“…1, 137.3, 132.9, 132.6, 129.4, 126.2, 124.8, 122.2, 120.3, 115.9, 115.5, 115.0 137.8, 134.7, 133.5, 132.8, 129.4, 129.2, 128.8, 127.3, 126.8, 126.1, 123.4, 121.4, 117.8, 116.4, 114.0, 51.2 3-(Phenylthio)-1H-pyrrolo[2,3-b]pyridine (1g-Int-1). 21 The title compound was prepared as described in procedure A using 7-aza indole (4.23 mmol, 1 equiv) as starting material. Yield: 695 mg, 72%, off-white solid.…”

“…IR (CH 2 Cl 2 , cm −1 ): 3128,3074,1528,1343,1153,737 3-(p-Tolylthio)-1H-indole (1j-Int-1). 21 The title compound was prepared as described in general procedure A using indole (4.268 mmol, 1 equiv) as starting material. Yield: 500 mg, 49%, white solid.…”

“…13 C{ 1 H} NMR (125 MHz, CDCl 3 ): δ (ppm) 140.7, 137.6, 137.0, 135.4, 133.7, 133.0, 132.7, 129.3, 128.8, 128.6, 127.3, 126.5, 124.6, 123.9, 122.6, 120.0, 115.1, 110.9, 51.1, 20 3-((4-Methoxyphenyl)thio)-1H-indole (1l-Int-1). 21 The title compound was prepared as described in general procedure A using indole (4.268 mmol, 1 equiv) as starting material. Yield: 350 mg, 32%, offwhite solid.…”

t BuOLi-promoted terminal alkyne functionalizations by aliphatic thiols and alcohols

“…Towards the synthesis of novel materials based on certain requirements, it is important to select appropriate noncovalent or weak or supramolecular interactions. 1 Use of these weak or noncovalent interactions like cation–π, 2 anion–π, 3 H-bonding, 4 halogen bonding, 5 S–H⋯π 6 sulfur⋯oxygen, 7 hydrophobic effects, 8 etc ., that have useful functions in organic synthesis, is also developing at a firm pace. 9 Especially, non-covalent interactions like S–H⋯S, S–H⋯O, O–H⋯S, N–H⋯S etc .…”

KOtBu-Promoted Halogen-Bond-Assisted Intramolecular C–S Cross-Coupling of o-Iodothioanilides for the Synthesis of 2-Substituted Benzothiazoles

“…Halogens, which are generally considered as sites of high electron density, adopt a Lewis acidic role on being covalently bound and, thus, interact with an electron-rich region of a neighboring atom or molecule (Lewis base) . This ability of the halogens to function as an electrophile has been exploited to a huge extent in fields such as soft matter, protein–ligand interactions, crystal engineering, medicinal chemistry, anion recognition, materials chemistry, and most importantly in organic synthesis and organocatalysis . Thus, keeping these factors in mind, a protocol for the intramolecular cross-coupling of ortho -iodothioanilides to result in the formation of benzothiazoles upon utilization of KO t Bu and phenanthroline was developed, wherein the aryl iodide is activated in the presence of a halogen bond between the units of ortho -iodothioanilide: the iodine atom of one unit (halogen bond donor-electron acceptor) and the sulfur atom of another unit (halogen bond acceptor–electron donor) (Scheme b).…”