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The synthesis of ether-functionalized molybdenum benzylidyne complexes [ArC-Mo{OC(CF3)2Me}3] (6, Ar = para-methoxyphenyl; 7, Ar = 2,4,6-trimethoxyphenyl) and of the sterically demanding benzylidyne complex [{2,4,6-(i-Pr)3C6H2}C-Mo{OC(CF3)2Me}3] are presented, together with their spectroscopic characterization, molecular structures, and catalytic activity in alkyne metathesis. Complexes 6 and 7 feature intermolecular contacts between the para-methoxy group and the molybdenum center that give rise to 1D-polymeric structures in the solid state. The preparation of other functionalized alkylidyne complexes, [ArC-Mo{OC(CF3)2Me}3] (Ar = 2-(i-PrO)C6H4, 8-MeO-Naph, 2,6-(i-Pr)2C6H3), was also attempted, but only the acyl precursors [ArC(=O)Mo(CO)5]- could be isolated. The synthesis of the molybdenum acyl complexes was challenging, and appropriate alternative protocols were developed.

Five new, intensely green diferrocenylphenylmethylium complexes 1+-5+ with electron donating (EDG: 4-MeO, 4-Me, 4-Br) or withdrawing (EWG: 3,5-CF3, 4-nC6F13) substituents were synthesized and fully characterized. The substituent influence on their electro

The reaction of (tBu)2ArP (1a-h), where the para position of the Ar group contains electron-donating or electron-withdrawing groups, with sulfated zirconium oxide partially dehydroxylated at 300 °C (SZO300) forms [(tBu)2ArPH][SZO300] (2a-h). The equilibrium binding constants of 1a-h to SZO300 are related to the pKa of [(tBu)2ArPH]; R3P that form less acidic phosphoniums (high pKa values) bind stronger to SZO300 than R3P that form more acidic phosphoniums (low pKa values). These studies show that Br?nsted acid sites on the surface of SZO300 are not superacidic.

Straightforward synthesis of benzosiloles was achieved by the invention of Pd/acid-catalyzed intramolecular anti-hydroarylation of aryloxyethynyl(aryl)silanes via ortho-C-H bond activation. The aryloxy group bound to the ethynyl carbon is the key factor for this transformation.

Nickel-catalyzed selective cross-coupling of aromatic electrophiles (bromides, chlorides, fluorides and methyl ethers) with organolithium reagents is presented. The use of a commercially available nickel N-heterocyclic carbene (NHC) complex allows the reaction with a variety of (hetero)aryllithium compounds, including those prepared via metal-halogen exchange or direct metallation, whereas a commercially available electron-rich nickel-bisphosphine complex smoothly converts alkyllithium species into the corresponding coupled product. These reactions proceed rapidly (1 h) under mild conditions (room temperature) while avoiding the undesired formation of reduced or homocoupled products. Nickel-catalyzed cross-coupling of aromatic electrophiles with organolithium reagents is presented. The use of a commercially available nickel N-heterocyclic carbene complex allows reaction with a variety of (hetero)aryllithium compounds, whereas a commercially available electron-rich nickel bisphosphine complex smoothly converts alkyllithium species into the corresponding coupled product.

An unprecedented CuI-catalysed cross-coupling of arylzirconium reagents with aryl and heteroaryl iodides is reported. Mechanistic studies with a Cp2ZrAr2 complex revealed that Cp2Zr(Ar)(Cl) is the reactive species that undergoes transmetalation with (PN-1)CuI. In addition, experiments with radical probes indicated that the reaction proceeds via a non-radical pathway. This journal is

The rational design, synthesis, and validation of a significantly improved insoluble polymer-supported siloxane-transfer agent has been achieved that permits efficient palladium-catalyzed cross-coupling reactions. The cross-linked polystyrene support facilitates product purification with excellent siloxane recycling. Drawbacks of a previous polymer-supported siloxane-transfer agent, relating to reaction efficiency and polymer stability after repeated cycles, have been addressed.

Diethylamidotitanium trichloride reacts with a variety of bulky amidines ArN(H)C(Ar′)NAr [Ar = 2,6-diisopropylphenyl; Ar′ = Ph, p-Me 2NC6H4, p-MeOC6H4, p-(2,5-dimethylpyrrole)C6H4/sub

The invention provides a compound of formula (I) or a pharmaceutically acceptable salt thereof, wherein Z, A, B, D,E, G, M1, M2, M3, M4, M5, M6, p, q, r, R3, R4, R5 and R6 are as defined in the specification. The invention also provides the use of such co

Several new tetraorganylborate salts have been synthesized by the addition of alkyl or phenyllithium reagents to a triorganylborane or organoboranylhalides. The chemical structure of the borates was confirmed by 1H, 13C NMR and IR spectroscopic measurements and elemental analysis. Solubility, spectroscopic and electrochemical properties of these salts have been investigated as well. The structures of the phenyltrialkylborates were varied systematically to control their oxidation potential. These compounds are the trimethyl-, triethyl-, n-tributyl- and sec-tributylborate derivatives and form a series of substituted phenyltrialkylborates containing either electron-withdrawing or electron-donating substituents in the para position of phenyl ring. The oxidation potential of these borates has been found to be a function of Hammett constant.

(Chemical Equation Presented) The relative basicities of aryllithiums bearing methoxy, chlorine, fluorine, trifluoromethyl and trifluoromethoxy substituents at the ortho, meta, and para positions have been assessed. To this end, two aryllithiums of compar

This invention relates to novel compounds having the structural formula I and to their pharmaceutically acceptable salt, compositions and methods of use. These novel compounds provide a treatment or prophylaxis of cognitive impairment, Alzheimer Disease, neurodegeneration and dementia.

The present invention relates to a class of melanocortin MCR4 agonists of general formula (I) wherein R1, R2, R3, R4 and R5 are as defined herein and especially to selective MCR4 agonist compounds, to

The reaction of different fluoroarenes 1 with lithium and a catalytic amount (7%) of naphthalene in THF at -30°C affords the corresponding aryllithium intermediates which, by reaction with several electrophiles at temperatures ranging between -30 and 0°C, lead to the expected products 2, after hydrolysis. (C) 2000 Elsevier Science Ltd.

A compound consisting of three aromatic moieties respectively bonded to a methyl carbocation, and a counterion; wherein each of the three aromatic moieties is optionally substituted with an electron-donating group, at least one of the three aromatic moiet

The reactions of (Rp)-menthyloxymethylphenylphosphine-borane with several organolithium reagents are described.Less sterically hindered reagents such as m-anisyllithium and p-anisyllithium react with the phospine-borane to afford the correspond

The enthalpies of (2-lithioaryl) ethers and that of 8-lithio-1-methoxynaphthyllithium in di-n-butyl ether are lower than those of their 4-lithio isomers by ca. 20 and 28 kJ/(mol RLi), respectively.

Whereas HgR2 (R=methyl or aryl) converts trans-(Ru(CO)2Cl2(PMe2Ph)2) exclusively into (Ru(CO)2R(Cl)(PMe2Ph)2) and does not react with cis-(Ru(CO)2Cl2(PMe2Ph)2), LiR reacts with either isomer to yield (Ru(CO)2R2(PMe2Ph)2) and also catalyses conversion of the trans isomer into the cis.The initial attack by R- is belived to be on a carbonyl ligand.Treatment of (Ru(CO)2R(Cl)(PMe2Ph)2) with LiR' yields mixed complexes (Ru(CO)2R(R')(PMe2Ph)2).In all cases the two organic ligands are mutually cis.The dimethyl complex undergoes reversible carbonylation to form mono- and di-acetyl complexes, and (Ru(CO)2Me(Ph)(PMe2Ph)2) also forms an acetyl coplex, but aryl ligands are unaffected by treatment with CO.

Initial measurements of the rate of reaction of bromobenzene with n-butyllithium in hexane solution have shown the exchange to be first order in bromobenzene and first order in n-butyllithium, with an activation energy of 12 kcal mol-1 (52 kJ mol-1).A Hammett relationship for the reaction of substituted bromobenzenes with n-butyllithium suggests negative charge character in the transition state (ρ ca 2).The addition of a Lewis donor (p-methylanisole) to the hexane solution was found to result in an increase in the rate of exchange, but did not affect the Hammett reaction constant.Several transition-state structures are considered; available evidence suggests that the exchange may be concerted, with either a four-centered structure, or SN2-type attack of the n-butyl anion at the bromine of the aryl bromide

Photooxygenations of 4-(2)H-anisole (3) and o-xylene (5) by 3-methylpyridazine 2-oxide (1) or pyridine 1-oxide (2) were studied in a variety of solvents at varying irradiation temperatures.Remarkable solvent effect on NIH-shift coupled with their hydroxylation processes was observed.