Palladium-catalyzed debenzylative cross-coupling of aryl benzyl sulfides with aryl bromides: synthesis of diaryl sulfides.

A novel debenzylative approach to synthesize diaryl sulfides from aryl benzyl sulfides and aryl bromides in good to excellent yields is reported. Mechanistic studies suggest a single catalyst, derived from Pd(dba)2 and NiXantPhos, efficiently catalyzes α-arylation of sulfides, C-S bond cleavage, and C-S bond formation in a tricatalytic cycle.

Chemo- and regioselective C(sp³)-H arylation of unactivated allylarenes by deprotonative cross-coupling.

The combination of aryl bromides, allylbenzene, base and a palladium catalyst usually results in a Heck reaction. Herein we combine these same reagents, but override the Heck pathway by employing a strong base. In the presence of LiN(SiMe3)2, allylbenzene derivatives undergo reversible deprotonation. Transmetalation of the resulting allyllithium intermediate to LPdAr(Br) and reductive elimination provide the 1,1-diarylprop-2-enes, which are not accessible by the Heck reaction. The regioselectivity in this deprotonative cross-coupling process is catalyst-controlled and very high.

Palladium-Catalyzed Direct α-Aryation of Benzyl Thioethers with Aryl Bromides.

The arylation of sp3-hybridized C-H's bonds is a powerful strategy to build molecular complexity and diversity. A novel and efficient palladium-catalyzed direct sp3 C-H arylation of aryl and alkyl benzyl thioether derivatives with aryl bromides is reported. The reaction involves reversible deprotonation of the benzylic C-H's of the thioether with either LiN(SiMe3)2 or NaN(SiMe3)2 and subsequent cross-coupling to provide the functionalized products in up to 97% yield. A screen of 24 of the most successful ligands in cross-coupling chemistry led to the identification of NiXantPhos as the only viable ligand for this challenging coupling.

Essential Oils from Different Plant Parts of Eucalyptus cinerea F. Muell. ex Benth. (Myrtaceae) as a Source of 1,8-Cineole and Their Bioactivities.

Eucalyptus cinerea, known as silver dollar tree, has few descriptions in traditional medicine. Chemical composition and antimicrobial properties of the essential oils of leaves, flowers and fruits, collected seasonally, were determined by GC/MS and disk diffusion/MIC, respectively. 1,8-Cineole was the main compound, particularly in fresh leaves-Spring (74.98%), dried leaves-Spring (85.32%), flowers-Winter (78.76%) and fruits-Winter (80.97%). Other compounds were found in the aerial parts in all seasons: α-pinene (2.41% to 10.13%), limonene (1.46% to 4.43%), α-terpineol (1.73% to 11.72%), and α-terpinyl acetate (3.04% to 20.44%). The essential oils showed antimicrobial activities against bacteria and yeasts, with the best results being found for the dried autumn and winter leaves oils (MIC < 0.39 mg/mL) against Streptococcus pyogenes. For the other tested microorganisms the following MIC results were found: Staphylococcus aureus-Dried leaves oil from summer (0.78 mg/mL), Pseudomonas aeruginosa-Flowers oil from autumn and fruits oil from winter (1.56 mg/mL) and Candida albicans-Flowers oil from autumn and fruits oils from winter and spring (0.78 mg/mL).