Norbornene

About: Norbornene is a research topic. Over the lifetime, 5628 publications have been published within this topic receiving 104495 citations. The topic is also known as: norbornylene & norcamphene.

Synthesis and activity of ruthenium olefin metathesis catalysts coordinated with thiazol-2-ylidene ligands.

Abstract: A new family of ruthenium-based olefin metathesis catalysts bearing a series of thiazole-2-ylidene ligands has been prepared. These complexes are readily accessible in one step from commercially available (PCy_3)_2Cl_2Ru CHPh or (PCy_3)Cl_2Ru CH(o-iPrO−Ph) and have been fully characterized. The X-ray crystal structures of four of these complexes are disclosed. In the solid state, the aryl substituents of the thiazole-2-ylidene ligands are located above the empty coordination site of the ruthenium center. Despite the decreased steric bulk of their ligands, all of the complexes reported herein efficiently promote benchmark olefin metathesis reactions such as the ring-closing of diethyldiallyl and diethylallylmethallyl malonate and the ring-opening metathesis polymerization of 1,5-cyclooctadiene and norbornene, as well as the cross metathesis of allyl benzene with cis-1,4-diacetoxy-2-butene and the macrocyclic ring-closing of a 14-membered lactone. The phosphine-free catalysts of this family are more stable than their phosphine-containing counterparts, exhibiting pseudo-first-order kinetics in the ring-closing of diethyldiallyl malonate. Upon removing the steric bulk from the ortho positions of the N-aryl group of the thiazole-2-ylidene ligands, the phosphine-free catalysts lose stability, but when the substituents become too bulky the resulting catalysts show prolonged induction periods. Among five thiazole-2-ylidene ligands examined, 3-(2,4,6-trimethylphenyl)- and 3-(2,6-diethylphenyl)-4,5-dimethylthiazol-2-ylidene afforded the most efficient and stable catalysts. In the cross metathesis reaction of allyl benzene with cis-1,4-diacetoxy-2-butene increasing the steric bulk at the ortho positions of the N-aryl substituents results in catalysts that are more Z-selective.

Reactions of gold(III) oxo complexes with cyclic alkenes.

Abstract: An auraoxetane , obtained from the reaction of norbornene with a gold( III ) oxo complex, has been isolated and fully characterized (see structure). Action of the olefin leads to elimination of the epoxide from the auraoxetane.

Catalytic investigation of rhodium nanoparticles in hydrogenation of benzene and phenylacetylene

Abstract: Nanoparticles of rhodium embedded in polyvinylpyrrolidone (PVP), as catalyst, were investigated in the hydrogenation of different substrates (benzene, phenylacetylene, norbornene, quinoline, adiponitrile). The solid was used as a heterogeneous catalyst or as a soluble heterogeneous catalyst in biphasic conditions (liquid/liquid) when the catalyst was dissolved in water. In both cases, the kinetics of the catalytic reaction were found to be zero-order in respect to the substrate and first-order with respect to hydrogen and catalyst. The higher hydrogenation reaction rate was found for benzene by using biphasic conditions. The [Rh-PVP] catalyst has shown an efficient activity for the catalytic hydrogenation of norbornene, quinoline and adiponitrile into norbornane, tetrahydroquinoline and 6-aminocapronitrile.

Olefin Polymerization and Ring-Opening Metathesis Polymerization of Norbornene by (Arylimido)(aryloxo)vanadium(V) Complexes of the Type VX2(NAr)(OAr`). Remarkable Effect of Aluminum Cocatalyst for the Coordination and Insertion and Ring-Opening Metathesis Polymerization

Abstract: Various (arylimido)(aryloxo)vanadium(V) complexes of the type VCl2(NAr)(OAr‘) [NAr = N-2,6-Me2C6H3 (2), N-2,6-iPr2C6H3 (3); OAr‘ = O-2,6-Me2C6H3 (a), O-2,6-iPr2C6H3 (b), O-2,6-tBu2-4-MeC6H2 (c)] have been prepared in high yields from VCl3(NAr) with Ar‘OH in n-hexane. 2b exhibited remarkable catalytic activity for ethylene polymerization in the presence of methylaluminoxane (MAO), affording high molecular weight polymer with unimodal molecular weight distribution (Mw = 2.92 × 106, Mw/Mn = 2.88). V(CH2Ph)2(N-2,6-Me2C6H3)(O-2,6-iPr2C6H3) (4) initiated ring-opening metathesis polymerization (ROMP) of norbornene without cocatalyst, affording high molecular weight polymer with unimodal molecular weight distribution (Mw = 4.69 × 106, Mw/Mn = 1.93). The ROMP also proceeded efficiently if 2b or 2c was treated with AlMe3 (5−10 equiv) in toluene, and high stereoregularity (trans/cis = 91/9) in the olefinic double bond for the resultant polymer was observed by 2b. On the other hand, remarkable catalytic activities by...