Search results for "metathesis"

Approaching a “naked” boryl anion: amide metathesis as a route to calcium, strontium, and potassium boryl complexes

2020

Abstract Amide metathesis has been used to generate the first structurally characterized boryl complexes of calcium and strontium, {(Me3Si)2N}M{B(NDippCH)2}(thf)n (M=Ca, n=2; M=Sr, n=3), through the reactions of the corresponding bis(amides), M{N(SiMe3)2}2(thf)2, with (thf)2Li‐ {B(NDippCH)2}. Most notably, this approach can also be applied to the analogous potassium amide K{N(SiMe3)2}, leading to the formation of the solvent‐free borylpotassium dimer [K{B(NDippCH)2}]2, which is stable in the solid state at room temperature for extended periods (48 h). A dimeric structure has been determined crystallographically in which the K+ cations interact weakly with both the ipso‐carbons of the flanki…

Bond stretching and redox behavior in coinage metal complexes of the dichalcogenide dianions [(SPh2P)2CEEC(PPh2S)2]2- (E=S, Se): diradical character …

2011

The metathetical reactions of a) [Li(tmeda)](2)[(S)C(PPh(2)S)(2)] (Li(2)·3c) with CuCl(2) and b) [Li(tmeda)](2)[(SPh(2)P)(2)CSSC(PPh(2)S)(2)] (Li(2)·4c) with two equivalents of CuCl both afford the binuclear Cu(I) complex {Cu(2)[(SPh(2)P)(2)CSSC(PPh(2)S)(2)]} (5c). The elongated (C)S-S(C) bond (ca. 2.54 and 2.72 A) of the dianionic ligand observed in the solid-state structure of 5c indicate the presence of diradical character as supported by theoretical analyses. The treatment of [Li(tmeda)](2)[(SPh(2)P)(2)CSeSeC(PPh(2)S)(2)] (Li(2)·4b) and Li(2)·4c with AgOSO(2)CF(3) produce the analogous Ag(I) derivatives, {Ag(2)[(SPh(2)P)(2)CEEC(PPh(2)S)(2)]} (6b, E=Se; 6c, E=S), respectively. The disele…

Highly convergent total synthesis of (+)-anaferine and (−)-dihydrocuscohygrine

2019

A unified and highly convergent total synthesis of anaferine and dihydrocuscohygrine alkaloids has been devised, taking advantage of the dual role of N-sulfinyl amines as nucleophilic nitrogen sources and chiral auxiliaries. A bidirectional cross metathesis reaction followed by a double intramolecular aza-Michael reaction led us to create the whole skeleton of the natural products in a very simple manner.

1977

The thermal behavior of cycloalkanes (CH2)n with 12 ≤ n ≤ 84 prepared by metathesis reaction of cyclododecene, GPC separation of the oligomers, and hydrogenation has been investigated. The molar enthalpies of fusion being lower by a certain amount than those of the corresponding n-alkanes are a linear function of the chain length n. The entropy of fusion per CH2 increases with chain length in a not-linear mode (when plotted vs. 1/n). The melting points of the cycloalkanes are lower than those of the corresponding n-alkanes, the difference becoming smaller with increasing chain length.

ChemInform Abstract: Asymmetric Allylation/Ring Closing Metathesis: One-Pot Synthesis of Benzo-Fused Cyclic Homoallylic Amines. Application to the Fo…

2013

A stepwise process consisting of asymmetric allylation of imines of type (I) and following ring-closing metathesis of the resulting dienes (III) is developed to synthesize cyclic homoallylic amines.

Strukturanalytische Untersuchungen P-substituierter 1,3,2-Diazaphospholidine

2011

2-Diphenylphosphanyl-1,3,2-diazaphospholidines were prepared via metathesis from 2-chloro-1,3,2-diazaphospholidines and LiPPh2. For some of the products, symmetrisation to tetraphenyldiphosphane and 2,2′-bis-1,3,2-diazaphospholidinyls was observed. Most of the derivatives were characterised by single-crystal X-ray diffraction, which showed that all compounds studied feature elongated exocyclic P–Cl or P–P-bonds, respectively. The extent of this bond lengthening is in the P-phosphanyl-substituted species similar and in the P-chloro-derivatives less pronounced than in corresponding CC-unsaturated 1,3,2-diazaphospholenes. Structure correlation involving comparison of exocyclic P–X and endocycl…

Copper‐Promoted Formation of Vinylsiloxanes

2020

The metathesis reactions of chlorovinylsilanes with copper(I) oxide are reported. The process is catalyzed by HCl which can be in situ generated via hydrolysis of chlorosilanes by traces of water present in the system. An appearance of olefin/CuCl π‐intermediates can provide a stereoselectivity of the process and alter the pathway of siloxanes formation employing Cu2O as the source of oxygen. It was also shown that acetonitrile may be available as a solvent for construction of the systems with large preparative capabilities, including those based on the use atmospheric oxygen in siloxane synthesis.

Sulphides of the platinum group elements—12. Bis(tetraphenylphosphonium) pentakaidekakissulphido platinates(IV)

1991

Abstract Synthetic routes to tetraphenylphosphonium salts of [PtSx]2− are outlined, where x = 15 or 18. Generally, (PPh4)2[Pt(S5)3] is formed most readily. The compound [(C6H5)4P]2[PtS15], always solvated, has been obtained by synthesis in acetonitrile (sulphur, triethylamine, H2S and [PPh4]2[PtCl6]) and by metathesis (in DMF) from the known hydrated ammonium compound (NH4)2[Pt(S5)3]2H2O+2[Ph4P]Br→(Ph4P)2[Pt(S5)3]· DMF+2NH4Br, and from the dismutation (in acetone) 3PtS172−→PtS152−+2PtS182−. X-ray diffraction shows that crystals obtained from DMF and acetone are the solvated salts [Ph4P]2· [Pt(S5)3]· S, with solvent molecules (S) uncoordinated. In both, the three platinopentathian rings rela…

Ionic Liquids: Media for Better Molecular Catalysis

2004

Ionic liquids (ILs) are more and more suggested as substitutes for traditional solvents in organic synthesis and catalysis. They are suitable candidates for the dissolution of ionic complexes. They can activate and retain them in a polar state: in fact, they act as sequestrands, opening the route to two-phase processes and easier catalyst recovery. This paper reviews authors' results with the development of new syntheses of ILs and applications in carbon–carbon bond formation (dimerisation of methyl acrylate) and redistribution (ring closing metathesis) reactions using ionic precatalysts.

Literary-Stylistic Metathesis in the Hebrew Bible

2020

Abstract Biblical scholarship has concentrated almost exclusively on cases of unintentional metathesis, particularly as a tool of textual criticism. But metathesis is not only a result of accidents and mistakes; it can also be deliberately employed as a literary-stylistic device. Accordingly, this study addresses all three of these categories of metathesis in the biblical literature, but focuses particularly on Literary-stylistic metathesis that is an intentional form of metathesis, in which an author or editor has deliberately chosen to use two or more words that share the same characters in inverse order.