Search

Six new naturally occurring diacetylenic spiroacetal enol ethers, Lactiflodiynes A–F (1–6), together with five known congeners (7–11), were isolated from the whole plant of Artemisia lactiflora (Compositae). The structures were elucidated by extensive spectroscopic methods, X-ray crystallography, chemical transformations, and CD. The absolute configuration of Lactiflodiyne A (1) was determined to be 2R, 5S, 6S, and 7R by an X-ray crystallographic diffraction experiment using Mo Kα radiation with the absolute parameter of 0.01(8). In combination with CD, the absolute configurations of compounds 2–11 were confirmed by chemical transformations using 1 as the starting material.

Air-stable secondary diaminophosphine sulfide preligands enable challenging nickel-catalyzed cross-coupling reactions of electron-deficient as well as electron-rich fluoro(hetero)arenes as electrophiles.

A palladium-catalyzed reaction sequence consisting of an intermolecular amination and an intramolecular direct arylation enabled highly regioselective syntheses of functionalized indoles or carbazoles and proved to be amenable to the use of inexpensive 1,2-dichloroarenes as electrophiles.

Magnesiumorganische Verbindungen konnen in einer Vielzahl nutzlicher Transformationen eingesetzt werden, die auch fur industrielle Prozesse von Bedeutung sind. Jungere Arbeiten zur Synthese hochfunktionalisierter Grignard-Reagenzien eroffnen hierbei faszinierende neue Perspektiven fur die organische Synthesechemie. Insbesondere der Zusatz uberstochiometrischer Mengen Lithiumchlorid erlaubt die Herstellung magnesiumorganischer Verbindungen ausgehend von Haloarenen oder Arenen unter sehr milden Reaktionsbedingungen. Diese hochfunktionalisierten Grignard-Reagenzien konnen als Startmaterialien fur ubergangsmetallkatalysierte Kreuzkupplungsreaktionen dienen. Neuere Entwicklungen im Ligandendesign resultieren in hochaktiven Palladium- und Nickelkatalysatoren fur effiziente Umsetzungen von preiswerten Chloriden und Tosylaten oder anspruchsvollen Fluoriden. Als okonomisch attraktive Alternative weisen eisenkatalysierte Kupplungsreaktionen magnesiumorganischer Verbindungen enormes Potential fur weitere Entwicklungen auf. Organomagnesium reagents can be employed for a variety of useful transformations, which are also of relevance for industrial processes. Recent protocols for syntheses of highly functionalized Grignard reagents highlight fascinating new perspectives for organic synthesis. Particularly, the addition of superstoichiometric amounts of LiCl allowed for the preparation of organomagnesium compounds, employing haloarenes or arenes at very mild reaction conditions. These highly functionalized Grignard reagents can be used as starting materials for transition metal-catalyzed cross-coupling reactions. New developments in the ligand design resulted in highly active palladium and nickel catalysts for efficient transformations of inexpensive chlorides or tosylates, as well as challenging fluorides. Economically attractive iron-catalyzed coupling reactions of organomagnesium reagents bear great potential for further developments.

Catalytic amounts of economically attractive [RuCl3(H2O)n] allow for direct arylations via C–H bond functionalization with aryl bromides under phosphine ligand-free reaction conditions. Thereby, a variety of functionalized (hetero)aryl bromides, bearing either electron-withdrawing or electron-releasing substituents, can be employed for direct arylations of pyridine, oxazoline, pyrazole, or ketimine derivatives as pronucleophiles.

Catalytic amounts of aromatic carboxylic acid MesCO H enabled efficient ruthenium-catalyzed direct arylations in apolar solvents with unparalleled broad scope via a concerted deprotonation-metalation mechanism.

Catalytic amounts of phosphoric acid diesters enabled highly efficient intramolecular hydroaminations of nonactivated alkenes. With an enantiomerically enriched Bronsted acid catalyst an unprecedented metal-free asymmetric hydroamination of a nonactivated alkene was accomplished.

Catalytic amounts of [RuCl 3 (H 2 O) n ] allow for direct -arylations via C-H bond functionalization with aryl bromides, -bearing a variety of important functional groups.

A one-pot synthesis of 2-aryl- and 2-vinylindoles based on a ruthenium-catalyzed hydroamination and a palladium-catalyzed intramolecular Heck reaction is reported. The ruthenium-catalyzed addition reaction was applied to terminal as well as internal alkynes. Intramolecular Heck reactions of the resulting 2-chloroanilino enamines were achieved using an in situ generated palladium complex derived from an N-heterocyclic carbene.

Studies on the use of easily accessible heteroatom-substituted secondary phosphine oxides as preligands for cross-coupling reactions are described. These air-stable sterically hindered phosphine oxides allow for efficient palladium-catalyzed Suzuki- and nickel-catalyzed Kumada-coupling reactions using electronically deactivated aryl chlorides. In addition, they enable nickel-catalyzed coupling reactions of magnesium organyls with aryl fluorides at ambient temperature, and ruthenium-catalyzed coupling reactions of aryl chlorides via C-H bond activation. Finally, the application of modular diamino phosphine chlorides as preligands for a variety of transition-metal-catalyzed C-C and C-N bond formation reactions employing electron-rich aryl chlorides is presented.

A palladium complex derived from a sterically hindered diaminochlorophosphine allowed for Suzuki-Miyaura cross-couplings of chloroarenes with ample scope and provided access to tetra-ortho-substituted bi(hetero)aryls.

Air-stable secondary diaminophosphine sulfide preligands enable challenging nickel-catalyzed cross-coupling reactions of electron-deficient as well as electron-rich fluoro(hetero)arenes as electrophiles.

A palladium complex derived from a sterically hindered diaminochlorophosphine allowed for Suzuki-Miyaura cross-couplings of chloroarenes with ample scope and provided access to tetra-ortho-substituted bi(hetero)aryls.

Catalytic amounts of aromatic carboxylic acid MesCO2H enabled efficient ruthenium-catalyzed direct arylations in apolar solvents with unparalleled broad scope via a concerted deprotonation−metalation mechanism.

Catalytic amounts of economically attractive [RuCl3(H2O)n] allow for direct arylations via C–H bond functionalization with aryl bromides under phosphine ligand-free reaction conditions. Thereby, a variety of functionalized (hetero)aryl bromides, bearing either electron-withdrawing or electron-releasing substituents, can be employed for direct arylations of pyridine, oxazoline, pyrazole, or ketimine derivatives as pronucleophiles.

Two distinct economical catalysts for intramolecular hydroaminations of electronically unactivated alkenes with basic amines are described, which are based on (a) group 4 metal halides under basic reaction conditions or (b) Bronsted-acid organocatalysts.

[reaction: see text] Air-stable and easily accessible PinP(O)H enables highly efficient palladium-catalyzed Kumada cross-coupling reactions of aryl tosylates. The in situ generated catalyst proved applicable not only to electron-rich and electron-poor carbocyclic tosylates but also to heterocyclic tosylates, such as pyridine and quinoline derivatives. The results described herein constitute the first use of air-stable secondary phosphine oxides as preligands for transition-metal-catalyzed coupling reactions between organometallic species and tosylates.

Studies on the use of easily accessible heteroatom-substituted secondary phosphine oxides as preligands for cross-coupling reactions are described. These air-stable sterically hindered phosphine oxides allow for efficient palladium-catalyzed Suzuki- and nickel-cat- alyzed Kumada-coupling reactions using electronically deactivated aryl chlorides. In addi- tion, they enable nickel-catalyzed coupling reactions of magnesium organyls with aryl fluo- rides at ambient temperature, and ruthenium-catalyzed coupling reactions of aryl chlorides via C-H bond activation. Finally, the application of modular diamino phosphine chlorides as preligands for a variety of transition-metal-catalyzed C-C and C-N bond formation reactions employing electron-rich aryl chlorides is presented.

A palladium complex derived from air-stable TADDOLP(O)H catalyzes efficiently Hiyama, Stille, Kumada and Suzuki cross-coupling reactions of aryl and vinyl chlorides.

Two selectively successive I/Cu exchange reactions performed with (Nphyl)CuLi allow the functionalization of indoles in positions 2 and 3. The 2,3-diketones prepared by this method can readily be converted to tricyclic heterocycles by standard methods.