Transition-Metal-Free Intramolecular <i>N</i>-Arylations

<i>N</i>-Substituted phenoxazines and related aza analogs have been prepared from <i>N</i>-acetylated aryloxy anilides by transition-metal-free, base-catalyzed cyclization reactions. In the presence of a mixture of 10 mol % of <i>N,N</i>′-dimethylethylenediamine (DMEDA) and 2 equiv of K₂CO₃ in toluene at 135 °C the products are obtained in high yields

<i>N</i>‑Trifluoromethylthiolated Sulfoximines

Air- and moisture-stable <i>N</i>-trifluoromethylthio sulfoximines have been prepared from <i>N</i>–H-sulfoximines via the corresponding <i>N</i>–Br derivatives in excellent yields. The two-step process starts with an easy-to-perform bromination at the sulfoximine nitrogen, followed by a reaction with silver trifluoro­methane­thiolate. A one-pot reaction sequence allows difficult to prepare products to be obtained

Tetrahydrobenzo[<i>c</i>]thieno[2,1‑<i>e</i>]isothiazole 4‑Oxides: Three-Dimensional Heterocycles as Cross-Coupling Building Blocks

Unprecedented three-dimensional heterocycles are introduced, and their scaffold functionalization is described. A robust synthetic method utilizing cheap commercially available starting materials leads to a wide range of products on gram scale. The product portfolio can be expanded by applying newly devised building blocks with relevance for automated parallel synthesis in cross-coupling reactions

Cobalt-Catalyzed Oxidation of the β‑O‑4 Bond in Lignin and Lignin Model Compounds

In this work we demonstrate the use of Co­(acac)₃ in combination with <i>N</i>-hydroxyphthalimide as an oxidant for the selective α-oxidation of the representative β-O-4 linkages in lignin model compounds. The oxidation reaction proceeds under mild conditions at 80 °C using 1,4-dioxane as the solvent and an oxygen atmosphere. The prior α-oxidation in the β-O-4 linkage of the lignin polymer is known to result in an easier cleavage of the adjacent C–O and C–C bonds because of a decrease in bond stability. Finally, the conditions were successfully transferred to kraft- and organosolv-lignin samples as proven by 2D-NMR (HSQC) experiments and gel permeation chromatography measurements

Mechanochemical Rhodium(III)-Catalyzed C–H Bond Amidation of Arenes with Dioxazolones under Solventless Conditions in a Ball Mill

A procedure for the direct mechanochemical rhodium­(III)-catalyzed C–H bond amidation of arenes with 1,4,2-dioxazol-5-ones as the nitrogen source has been developed. The transformation proceeds under solventless conditions and does not require additional heating. The corresponding <i>ortho</i> amidated products are formed in high yields and in shorter reaction times than in solution

Nondirected Copper-Catalyzed Sulfoxidations of Benzylic C–H Bonds

A copper-catalyzed sulfoxidation of benzylic C–H bonds by nondirected oxidative C­(sp³)-H activation was developed. The process proceeds via sulfenate anions, which are generated by base-triggered elimination of β-sulfinyl esters and benzyl radicals. The functional group tolerance is high, and the product yields are good

Transition-Metal-Free Synthesis of Oxindoles by Potassium <i>tert</i>-Butoxide-Promoted Intramolecular α-Arylation

Potassium <i>tert</i>-butoxide-mediated intramolecular α-arylations of fluoro- and chloro-substituted anilides provide oxindoles in DMF at 80 °C. In this manner, diversely substituted products have been obtained in moderate to high yields

Exploring the Reactivity of <i>N</i>‑Alkynylated Sulfoximines: Regioselective Hydroacyloxylations and Hydroaminations

<i>N</i>-Alkynylated sulfoximines undergo smooth transformations with benzoic acids and sulfonamides under mild conditions affording the corresponding hydroacyloxylation or hydroamination products. The transformations proceed in the absence of catalysts or additional reagents in short reaction times generating the products in excellent yields and very high stereoselectivities

Silver-Mediated <i>N</i>‑Trifluoromethylation of Sulfoximines

An unprecedented approach to <i>N</i>-trifluoromethylations of electron-rich nucleophilic sites following a radical pathway is reported. Accordingly, various sulfoximines (19 examples) have been <i>N</i>-trifluoromethylated, providing previously unreported products with satisfying functionality tolerance in moderate to good yields. With a C–N bond length at the N–CF₃ moiety of 1.341 Å the respective linkage is shorter than a traditional C–N single bond and comparable with that of a C–N double bond

Copper-Catalyzed Oxidative Decarboxylative Couplings of Sulfoximines and Aryl Propiolic Acids

A method has been developed for the preparation of <i>N</i>-alkynylated sulfoximines involving the copper-catalyzed decarboxylative coupling of sulfoximines with aryl propiolic acids. A range of substituents on both the sulfoximidoyl moiety and the aryl group of the propiolic acid were compatible with this reaction process to afford a series of sulfoximidoyl-functionalized alkynes