A unique family of N-heterocyclic carbenes derived from bioxazolines (IBiox) suitable for application in transition-metal catalysis is described. The ligands are electron rich, sterically demanding, and have restricted flexibility. Their usefulness has been demonstrated the Suzuki−Miyaura cross-coupling hindered aryl chlorides boronic acids. For first time, tetraortho-substituted biaryls with methyl larger ortho-substituents synthesized using method.

A series of unprecedented organoiron complexes the formal oxidation states -2, 0, +1, +2, and +3 is presented, which are largely devoid stabilizing ligands and, in part, also electronically unsaturated (14-, 16-, 17- 18-electron counts). Specifically, it shown that nucleophiles unable to undergo beta-hydride elimination, such as MeLi, PhLi, or PhMgBr, rapidly reduce Fe(3+) Fe(2+) then exhaustively alkylate metal center. The resulting homoleptic organoferrate [(Me 4Fe)(MeLi)][Li(OEt 2)] 2 (...

A juggling act: The steric bulk of the ligand enhances reductive elimination in Pd-catalyzed Suzuki cross-coupling. However, it impedes oxidative addition and transmetallation sterically hindered substrates. This dilemma is solved with carbene 1, which exhibits flexible bulk. Supporting information for this article available on WWW under http://www.wiley-vch.de/contents/jc_2002/2003/z51325_s.pdf or from author. Please note: publisher not responsible content functionality any supporting...

Carbophilic Lewis acids can polarize a coordinated π-bond by slippage mechanism. A series of stable ylid- or enolate gold complexes ene-1,1-diamines not only emulate this property, but also reveal the exceptional donor capacity such electron-rich olefin ligands. Moreover, first metal complex tetraaminoallene is reported, which features prototype “carbodicarbene” ligand bound to transition-metal template.

Exchange of one PCy3 unit the classical Grubbs catalyst 1 by N-heterocyclic carbene (NHC) ligands leads to "second-generation" metathesis catalysts superior reactivity and increased stability. Several complexes this type have been prepared fully characterized, six them X-ray crystallography. These include unique chelate 13 14 in which NHC- Ru-CR entities are tethered form a metallacycle. A particularly favorable design feature is that such can be easily adjusted changing electronic steric...

The first defined complex for oligo- and polymerization of ethylene which requires no co-catalyst is the crystalline nickel (1). Its structure was established by X-ray analysis. Dissolved in toluene, compound (1) reacts with (50 bar) at 50°C giving almost exclusively linear α-olefins; polyethylene formed under a different set conditions.

Triphenylsilanolate ligands were found to impart excellent reactivity and outstanding functional group tolerance on molybdenum alkylidyne complexes, which catalyze alkyne metathesis reactions of all sorts. The active species either can be obtained in high yield by adaptation the established synthesis routes leading Schrock alkylidynes or generated situ from nitride complex 11, itself is readily accessible large quantity inexpensive sodium molybdate. Complexation silanolate complexes 12 24...

Reaction of ferrocene with lithium in the presence either ethylene or COD allows Fe(0)-ate complexes 1 and 4 to be prepared on a large scale, which turned out excellent catalysts for variety Alder-ene, [4+2], [5+2], [2+2+2] cycloadditon cycloisomerization reactions polyunsaturated substrates. The structures ferrates solid-state reveal capacity reduced iron center share electron density ligand sphere. This feature, coupled kinetic lability bound olefins, is thought responsible ease different...

The tail makes the difference: Removing isopropylidene acetal unit from well-known TADDOL ligands improved performance of derived phosphoramidite in asymmetric gold catalysis (see scheme; Ts=4-toluenesulfonyl). X-ray crystallography showed that binding pocket has an effective threefold symmetry, with through-space interactions between arene rings ligand and center.

Large spin-orbit coupling (SOC) is an intrinsic property of the heavy elements that directly affects electronic structures compounds. In this work, we report synthesis and characterization a monocoordinate bismuthinidene features rigid bulky ligand. All magnetic measurements [superconducting quantum interference device (SQUID), nuclear resonance (NMR)] point to diamagnetic compound. However, multiconfigurational chemical calculations predict ground state compound be dominated (76%) by spin...

The introduction of a single C-atom into organic substrates typically results in the formation flat molecules containing unsaturated C(sp)-centers. Adding C(sp3)-atom surrounded by four σ-C-C bonds, which opens up three-dimensional space, is an unresolved problem synthetic chemistry. We report synthesis and application diazosulfur ylide Ph2S=C=N2 reagent that combines reactivity both sulfur ylides diazo compounds to create carbon spiro-centers general fashion sequential or single-step...

A highly enantioselective Brønsted acid catalyzed direct synthesis of cyclic aminals from aldehydes has been developed. The methodology applied to the first asymmetric several antihypertensive aminal drugs including (R)-Thiabutazide.

Click chemistry has been utilized to access 2,6-bis(1-aryl-1,2,3-triazol-4-yl)pyridines (BTPs) as versatile extended heteroaromatic building blocks for their exploitation in supramolecular chemistry, particular foldamer and ligand design. In addition high-yielding synthesis using Cu(I)-catalyzed Huisgen-type 1,3-dipolar cycloaddition reactions the formed triazole moieties constitute an integral part of BTP framework encode both its pronounced conformational preferences well chelating...

Enantiomerically pure imidazolium triflates can be readily prepared from bioxazolines and oxazolineimines; deprotonation of triflate 2 gives a chiral N-heterocyclic carbene that act as ligand in catalytically active palladium complex.

A concise approach to a family of potent herbicidal 10-membered lactones is described on the basis ring-closing metathesis (RCM) as key step for formation medium-sized ring. This includes first total syntheses herbarumin I (1) and II (2) well synthesis several possible macrolides pinolidoxin series. comparison their spectral analytical data with those natural product allowed us establish stereostructure pinolidoxin, inhibitor induced phenylalanine ammonia lyase (PAL) activity, shown in 46....

Up to four stereocenters can be created efficiently in a single step by the asymmetric hydrogenation of oxazolidinone-substituted pyridines (see scheme). Furthermore, selective chirality transfer and nondestructive cleavage chiral auxiliary occur under same reaction conditions, making an additional unnecessary.

Nitride- and alkylidyne complexes of molybdenum endowed with triarylsilanolate ligands are excellent (pre)catalysts for alkyne-metathesis reactions all sorts, since they combine high activity an outstanding tolerance toward polar and/or sensitive functional groups. Structural reactivity data suggest that this promising application profile results from a favorable match between the characteristics high-valent center electronic steric features chosen Ar(3)SiO This interplay ensures...

Readily available phosphoramidites incorporating TADDOL-related diols with an acyclic backbone turned out to be excellent ligands for asymmetric gold catalysis, allowing a number of mechanistically different transformations performed good outstanding enantioselectivities. This includes [2 + 2] and [4 cycloadditions ene-allenes, cycloisomerizations enynes, hydroarylation reactions formation indolines, as well intramolecular hydroaminations hydroalkoxylations allenes. Their preparative...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCrystallization of Large Planar Polycyclic Aromatic Hydrocarbons: The Molecular and Crystal Structures Hexabenzo[bc,ef,hi,kl,no,qr]coronene Benzo[1,2,3-bc:4,5,6-b'c']dicoroneneRichard Goddard, Matthias W. Haenel, William C. Herndon, Carl Krueger, Maximilian ZanderCite this: J. Am. Chem. Soc. 1995, 117, 1, 30–41Publication Date (Print):January 1995Publication History Published online1 May 2002Published inissue 1 January...

Carbophile Lewis-Säuren können eine koordinierte π-Bindung nach einem Gleitmechanismus polarisieren. Eine Reihe stabiler Ylid- oder Enolat-Goldkomplexe von En-1,1-diaminen ahmt diese Eigenschaft und offenbart die außergewöhnliche Donorwirkung solcher elektronenreicher Olefinliganden. Zudem wird vom ersten Metallkomplex eines Tetraaminoallens berichtet; dieser enthält einen prototypischen, an ein Übergangsmetalltemplat gebundenen "Carbodicarben"-Liganden. Supporting information for this...

As mimics of α-amino acids, phosphonates have great promise as antibacterial and anti-HIV agents well protease inhibitors. Racemic α-branched aldehydes react, in the presence new chiral phosphoric acid catalyst 1, directly with p-anisidine (PMPNH2) a phosphite to furnish β-branched highly diastereoselectively enantioselectively. Anth=anthracenyl.

Your wish is my command: Deracemization a powerful strategy wherein racemate converted into 100 % yield of single enantiopure product. A new concept in catalytic deracemization presented, which with n stereogenic elements can be selectively each one 2(m) (m = number chiral centers the product) different products, by simple tuning reaction conditions.

Owing to its tremendous preparative importance, rhodium carbene chemistry has been studied extensively during past decades. The invoked intermediates have, however, so far proved too reactive for direct inspection, and reliable experimental information extremely limited. A series of X-ray structures pertinent this type, together with supporting spectroscopic data, now closes gap provides a detailed picture the constitution conformation such species. All complexes were prepared by...