C–H Halogenation of Pyridyl Sulfides Avoiding the Sulfur Oxidation: A Direct Catalytic Access to Sulfanyl Polyhalides and Polyaromatics

Abstract

Palladium-catalyzed oxidative C–H halogenation and acetoxylation reactions of S-unprotected sulfides, selectively directed by pyridinyl groups, allows the formation of C–X bonds (X = I, Br, Cl, OAc) by using simple halosuccinimide or phenyliodine diacetate (PIDA) oxidants. The undesired formation of sulfoxides and/or sulfones, which are usually observed under oxidative conditions, is fully obviated. Under the solvent-dependent conditions that we proposed, sulfide C–H functionalization is achieved in less than 1 h without any direct electrophilic halogenation at the pyridine moiety. N-Directed ortho-C–H activation of aryl also facilitates dibromination reactions which are hardly accessible with sulfone and sulfoxide counterparts because of their higher structural rigidity. This general method gives a straightforward access to polyhalide sulfides, without an organosulfur reduction step or protection–deprotection sequence. Polyhalide sulfides are valuable synthons that give a practical entry to new constrained polyaromatic and biphenyl sulfides, including synthetically challenging unsymmetrical examples.

Palladium‐Catalyzed C−H Iodination of Arenes by Means of Sulfinyl Directing Groups

“…[8] Although Roger and Hierso recently accomplished ortho-C-H halogenation and acetoxylation of aryl sulfides, a 2pyridyl group should be attached onto the sulfur atom as a directing and electron-withdrawing group. [9] We recently developed peri-selective C-H alkoxylation by means of sulfinyl directing groups of high compatibility with oxidative conditions. In the presence of a palladium catalyst and a hypervalent iodine reagent as an oxidant, peri-selective C-H fluoroalkoxylation of aryl sulfoxides has been accomplished.…”

Nanocatalysts for High Selectivity Enyne Cyclization: Oxidative Surface Reorganization of Gold Sub-2-nm Nanoparticle Networks

“…No reaction was observed after 16 h. Assuming that catalytically active surface cationic gold­(I) species were insufficiently present and/or inaccessible, we achieved further oxidation process on Ad-S@AuNPs 150%, BAd-S@AuNPs 50%, and DAd-S@AuNPs 50%. The gold NPs were treated with the organic oxidation agents phenyliodine­(III) diacetate (PIDA, 70 °C, 18 h) or meta -chloroperoxybenzoic acid ( m- CPBA) at 20 °C for 2 h, avoiding the addition of silver salts. To the best of our knowledge, little is known on the effects of such type of oxidative treatment on thiolated Au NPs. − We analyzed by XPS the resulting materials, as exemplified for the oxidized Ox-DAd-S@AuNPs 50% (Figure ).…”

Alkali halides as nucleophilic reagent sources for N-directed palladium-catalysedortho-C–H halogenation ofs-tetrazines and other heteroaromatics

“…Following this strategy, our group and others illustrated the efficiency of palladium catalysts for the ortho -halogenation on different N-containing heteroarenes, including challenging substrates of high nitrogen-content. 5,6…”