To obtain the supported catalysts, amorphous al2o3 is suspended in a solution of the respective ruthenium complex and ionic liquid in tetrahydrofuran and stirred at room temperature for 4 hours tetrahydrofuran is then evaporated under vacuum and the resulting material is rinsed with anhydrous diethyl ether twice before. Cycle b conjugate addition and metathesis set the stage for an lowed by ring- closing metathesis and reduction of the lactam afforded 72% er = 985:15 asymmetric pauson–khand reaction allylmagnesium chloride (3 equiv) cui (3 equiv) licl (3 equiv) tmscl (11 equiv) thf, –10 °c to rt 91% otbs a b c d ru. The living polymerization of ndca derivative containing the bulkiest substituent ( m4) catalyzed by g3 in tetrahydrofuran was confirmed by the kinetic studies with low polydispersity indices (pdi) ( 130) by using sequential romp, well-defined diblock copolymers containing anhydride groups were synthesized. The solvents typically used for olefin metathesis reactions, such as ch2cl2, 1,2- dichloroethane, and toluene, are immiscible with water, so we resorted to water- miscible solvents tetrahydrofuran (thf), used previously as a solvent for romp and acyclic diene metathesis with varying success, failed as a. Applicability of 2-methyltetrahydrofuran for olefin metathesis was examined with a set of ruthenium hoveyda-type second generation catalysts influence of temperature was studied and the results were compared with those obtained in classical solvents for metathesis: dichloromethane and toluene.
Abstract: a tandem olefin metathesis/oxidative cyc- lization has been developed to synthesize 2,5-disubstituted tetrahydrofuran (thf) diols in a stereocontrolled fashion from simple olefin precursors the ruthenium metathesis catalyst is converted into an oxidation catalyst in the second step and is thus. Bis(thiolate)(8) in tetrahydrofuran at 22oc this new catalyst was able to polymerize norbornene (9) with 92% yield and 98% of z-selectivity in one hour 2, 5 scheme 3 synthesis of the ruthenium catalyst 6 from commercial catalyst 7 another challenge in cross-metathesis chemistry is the increase of the. Here we report catalytic z-selective cross-metathesis reactions of terminal enol ethers, which have not been reported previously, and of allylic amides, used until in a 25-ml round-bottom flask equipped with a stir bar, the resulting residue was treated with (n-bu)4nf (10 m in thf, 210 ml, 210 mmol), and stirred for 2 h. Derivatives, as well as the mechanistically related metathesis polymerization of phenylacetylene (pa), is presented our results show that addition of a silver salt (agbf4) is necessary for the activation of the ditungsten complex polymerization of pa proceeds smoothly in tetrahydrofuran (thf) producing.
Conditions for reactions with 8b: nai (25 equiv relative to catalyst) and 8a in thf (0055 m in triene) for 1 h at rt, then add triene and stir for 2 h at 40 °c conditions for reactions with 18a: triene, ch2cl2 (0055 m in triene), and 18a for 2 h at 40 °c a enantiomeric excesses determined by chiral gc b determined by 1h nmr. Changing the solvent to toluene (entry 15) had no impact, while an improvement was noted in both thf (entry 16) and in diethyl ether (entry 17) better results were obtained by diluting the latter ethereal mixture from 05 m to 01 m (entry 19) ultimately, running the reaction at 35 °c in refluxing et2o for.
The term “olefin metathesis” was coined by calderon and displays a catalytic reaction where “olefins undergo bond reorganization, resulting in a both pre- catalysts 6 and 7 show high solubility in water and methanol, while they are insoluble in organic solvents, such as thf, ethanol, benzene or acetone. The reaction of tertiary 1,4- and 1,5-diols with cerium ammonium nitrate at room temperature gives tetrahydrofuran and tetrahydropyran derivatives in high yield and which are efficient catalyst precursors for ring-opening metathesis polymerization, ring-closing metathesis and enyne metathesis of a variety of substrates.
(coordinating/nucleophilic), avoid if possible (strongly coordinating) pentane, hexane, etc meoh, iproh, etc acetonitrile benzene, toluene, etc acetone, dmso tbme, et2o, thf, etc dmf ch2cl2, clch2ch2cl, phcl, etc neutral/ acidic water, pyridine etoac, hoac, iproac, etc free amines basic water. Bno h 4 equiv thf, reflux 50% yield nicolaou et al j am chem soc 1996, 118, 10335 □ schrock's molybdenum and tungsten catalyst can also mediate olefin metathesis/ carbonyl olefination o(ch2)3ph o [mo] o r [mo] o r o( ch2)3ph 86% yield fu, gc grubbs, rh jacs 1993, 115, 3800. Closure of the tetrahydrofuran had been accomplished in the conversion of prelaureatin to laurallene by murai11 and had been reproduced in our recent laurallene synthesis2 the assembly of the core nine-membered ether was to be accomplished through a ring closing metathesis reaction of an a,v-diene that contained. A tandem olefin metathesis/oxidative cyclization has been developed to synthesize 2,5-disubstituted tetrahydrofuran (thf) diols in a stereocontrolled fashion from simple olefin precursors the ruthenium metathesis catalyst is converted into an oxidation catalyst in the second step and is thus responsible for.
ring opening metathesis polymerization of norbornene and derivatives by the triply bonded ditungsten complex na[w2(μ-cl)3cl4(thf)2] thf)3 g floros, n saragas, p paraskevopoulou, n psaroudakis, s koinis, m pitsikalis, n hadjichristidis and k mertis polymers, volume 4, issue 4, pages 1658-1673, ( 2012. Generated by stirring 2a-5a (4 mol %) in thf with 25 equiv of nai b enantiomeric excesses determined by chiral gc see supporting informa- tion for chromatograms and proof of absolute stereochemistry c determined by 1h nmr spectrum of crude reaction mixture ring-closing olefin metathesis catalysts articles. Cyclopropene polymerization and enyne metathesis catalyzed by high oxidation state molybdenum alkylidenes an x-ray study of [(thf)((cf3)2meco)2(arn) moch]2-1,4-c6h4 (thf = tetrahydrofuran ib), which is closely related to la, showed it to be the expected bimetallic species in which each end is approximately a.