Asymmetric Copper-Catalyzed Vinylogous Mukaiyama Michael Addition of Cyclic Dienol Silanes to Unsaturated α-Keto Phosphonates.

A highly stereoselective vinylogous Mukaiyama Michael reaction (VMMR) leading to α-keto phosphonate-containing γ-butenolides with two stereogenic centers is described. The presented transformation is catalyzed by a combination of a commercially available C2 -symmetric bisoxazoline (BOX) ligand and a copper salt and tolerates a variety of nucleophiles and electrophiles. The stereoselectivities of the reactions are good to excellent and the products are obtained in moderate to high yields.

A mild, ferrocene-catalyzed C-H imidation of (hetero)arenes.

A simple method for direct C-H imidation is reported using a new perester-based self-immolating reagent and a base-metal catalyst. The succinimide products obtained can be easily deprotected in situ (if desired) to reveal the corresponding anilines directly. The scope of the reaction is broad, the conditions are extremely mild, and the reaction is tolerant of oxidizable and acid-labile functionality, multiple heteroatoms, and aryl iodides.

Catalytic, asymmetric synthesis of phosphonic γ-(hydroxyalkyl)butenolides with contiguous quaternary and tertiary stereogenic centers.

A procedure that enables high yielding access to phosphonic γ-(hydroxyalkyl)butenolides with excellent regio-, diastereo- and enantiocontrol is reported. The simultaneous construction of up to two adjacent quaternary stereogenic centers by a catalytic asymmetric vinylogous Mukaiyama aldol reaction unites biologically and medicinally relevant entities, namely α-hydroxy phosphonates and γ-(hydroxyalkyl)butenolides. This is achieved by utilizing a readily available chiral copper-sulfoximine catalyst showing a broad functional group tolerance for both the electrophilic and nucleophilic reactants.

Base-catalyzed synthesis of substituted indazoles under mild, transition-metal-free conditions.

Back to basics: A transition-metal-free method developed for the synthesis of indazoles involves an inexpensive catalytic system composed of a diamine and K2CO3. Various (Z)-2-bromoacetophenone tosylhydrazones were converted into indazoles at room temperature in excellent yields (see example; Ts = p-toluenesulfonyl). The yield was improved by photoisomerization with UV light when E/Z isomeric mixtures of the starting material were used.

Synthesis of chiral sulfoximine-based thioureas and their application in asymmetric organocatalysis.

For the first time, chiral sulfoximine derivatives have been applied as asymmetric organocatalysts. In combination with a thiourea-type backbone the sulfonimidoyl moiety leads to organocatalysts showing good reactivity in the catalytic desymmetrization of a cyclic meso-anhydride and moderate enantioselectivity in the catalytic asymmetric Biginelli reaction. Straightforward synthetic routes provide the newly designed thiourea-sulfoximine catalysts in high overall yields without affecting the stereohomogeneity of the sulfur-containing core fragment.

Transition-metal-free intramolecular N-arylations.

N-Substituted phenoxazines and related aza analogs have been prepared from N-acetylated aryloxy anilides by transition-metal-free, base-catalyzed cyclization reactions. In the presence of a mixture of 10 mol % of N,N'-dimethylethylenediamine (DMEDA) and 2 equiv of K(2)CO(3) in toluene at 135 °C the products are obtained in high yields.

Trace metal impurities in catalysis.

Metal-catalysed transformations are a powerful tool in organic chemistry and the enormous progress, which has been made in the last few decades, was one more time honoured by the Nobel Prize in Chemistry in 2010. Many metal-containing compounds have been applied in carbon-carbon and carbon-heteroatom bond formations. However, not every component originally claimed as catalyst turned out to be the active ingredient in the end.

Novel pyridinium dyes that enable investigations of peptoids at the single-molecule level.

Single-molecule microscopy is a powerful tool for investigating various uptake mechanisms of cell-penetrating biomolecules. A particularly interesting class of potential transporter molecules are peptoids. Fluorescence labels for such experiments need to comply with several physical, chemical, and biological requirements.