Synlett

A triazine-based reagent, 2-hydroperoxy-4,6-dimorpholino-1,3,5-triazine (Triazox-II), was developed for alkene epoxidation. This reagent can be prepared from inexpensive starting materials (cyanuric chloride and morpholine) on a 15 mmol scale in two steps with 54% overall yield and isolated as a pure, bench-stable solid with low sensitivity to impact and friction. Triazox-II exhibited higher solubility in chlorinated solvents than the previously reported reagent Triazox. Epoxidation using Triazox-II was conducted in various solvents, with a preference for CH2Cl2 at 0.5 M concentration, resulting in epoxides in 83–94% yield. The reaction was conducted under mild conditions owing to the low acidity of the reaction coproduct.

The fusion of transition-metal catalysis with radical chemistry provides a versatile platform for the asymmetric radical carboazidation of alkenes to enable the rapid assembly of highly functionalized chiral azide compounds. Here, we present an iron-catalyzed asymmetric three-component radical carboazidation that processes electron-deficient alkenes by direct activation of aliphatic C–H bonds. This strategy provides access to a range of valuable chiral azides from readily available chemical feedstocks bearing a tetrasubstituted carbon stereocenter, and their synthetic potential is further showcased through straightforward transformations to provide other valuable enantioenriched building blocks.

Chemical synthesis of octasaccharide motif from cranberry arabinoxyloglucan oligosaccharides with antiadhesion activities has been achieved for the first time. Synthetic approach highlights the following features: 1) stereoselective constructions of 1,2-cis-Xyl bonds via the combination of reagent modulation and remote participation; 2) modular [1+3+1+3] orthogonal one-pot assembly of the target octasaccharide on the basis of glycosyl ortho-(1-phenylvinyl)benzoate, which avoids the issues such as aglycone transfer associated with one-pot glycosylation based on thioglycosides.

In this study, a pentacyclic keto-olefin was treated with thallium(III) nitrate trihydrate, resulting in the formation of mono ring-expanded product. However, when the corresponding dialkene was treated with thallium(III) nitrate trihydrate, an unexpected ring-closure product was obtained instead of the expected double ring-expanded product. The use of the Tebbe reagent facilitated the olefination of hindered and enolizable cage dione derivatives, converting both keto moieties into methylene groups and forming the desired diolefin. Notably, conventional Wittig reagents proved to be ineffective in the olefination sequence with cage diones.

Numerous reports invoke CuIII–F intermediates engaging in oxidative cross-couplings mediated by low/mid-valent copper and formal sources of ‘F+’ oxidants. These elusive and typically instable CuIII fluorides have been rarely characterized or spectroscopically identified, making their existence and participation within catalytic cycles somehow questionable. We have authenticated a stable organocopper(III) fluoride that undergoes Csp–CF3 bond formation upon addition of silyl-capped alkynes following a 2 e– CuIII/CuI redox shuttle. This finding strongly supports the intermediacy of CuIII fluorides in C–C coupling. We review herein the state of the art about well-defined CuIII fluorides enabling cross-coupling reactions.1 Introduction2 Brief History of Coupling-Competent CuIII Fluorides3 Design of an Isolable – yet Reactive – Organocopper(III) Fluoride4 Alkyne Trifluoromethylation: Scope and Mechanism5 Extension to Aryl–CF3 and C–Heteroatom Couplings6 Summary and Outlook

Indium(III) triflate was found to be an efficient metal catalyst for the electrophilic substitution reaction of substituted indoles with various isatins or aryl aldehydes in acetonitrile solvent to afford the corresponding 3,3-diaryloxindoles or bis(indol-3-yl)methanes, respectively, in high yields at room temperature. This new procedure has remarkable features such as experimental simplicity, high conversions, good to excellent yields, short reaction times, and simple workup procedures

We herein developed a base-promoted cyclization reaction between N-acyl benzotriazoles and p-toluenesulfonylmethyl isocyanide (TosMIC) to afford 4,5-disubstituted oxazoles. In the presence of 3 equiv of K3PO4, the two readily available starting materials reacted in N,N-dimethylformamide at 80 °C to give 28 examples of 4-tosyl-5-aryl, -alkyl, or -alkenyl-substituted oxazoles in moderate to high yields.

We report a practical scalable synthesis of the natural product (±)-tylophorine by using an operationally simple protecting-group-free route from readily accessible starting materials. Synthesis of a cyclic N-acetyl diester compound through cyclization, followed by two key steps (decarboxylation and a Clemmensen reduction), provides access to the target molecule.

The selective construction of two C(sp3)–C(sp3) bonds through trimolecular cross-coupling of unactivated alkenes remains one of the most difficult challenges in organic synthesis. Despite previous advances in metal-catalyzed coupling for the dicarbofunctionalization of alkenes, dialkylation is still problematic due to the instability of the requisite metal–alkyl intermediate, which undergoes facile β-hydride elimination or protodemetalation. Recently, our group was successful in developing a bimolecular homolytic substitution (SH2) strategy that circumvents metal–alkyl side reactions and accomplishes the challenging cross-coupling of metal–alkyl intermediates with alkyl radicals in the absence of a directing auxiliary, permitting a highly regioselective dialkylation of unactivated alkenes.1 Introduction2 Nickel-Catalyzed Dicarbofunctionalization of Unactivated Alkenes3 Nickel-Catalyzed Dialkylation of Unactivated Alkenes4 Conclusions and Perspectives

An enzymatic method was developed for the synthesis of fluorene derivatives by benzannulation of indene dienes with benzoylacetonitrile in a nonaqueous solvent. Under the optimal reaction condition [indene diene (0.5 mmol), benzoylacetonitrile (0.5 mmol), ethanol (2 mL), lipase from porcine pancreas (5 mg), 50 °C, 24 h], fluorenes bearing various groups were obtained in satisfactory yields (83–93%). This method not only offers a significant advancement in the synthesis of fluorene derivatives, but also represents a new application of lipase in promiscuous enzyme catalysis.