6972-81-2Relevant articles and documents
Fast olefin metathesis: Synthesis of 2-aryloxy-substituted Hoveyda-type complexes and application in ring-closing metathesis
Kos, Pavlo,Savka, Roman,Plenio, Herbert
, p. 439 - 447 (2013/05/21)
Four 1-(4-R-phenoxy)-2-ethenylbenzenes (R=NMe2, H, Cl, NO 2) 4a, 4b, 4c and 4d were reacted with the ruthenium complexes [RuCl2(NHC)(3-phenylindenylidene)(py)] in the presence of a protic resin to result in the formation of the respective Hoveyda-type complexes 5a-d {NHC=SIMes [1,3-bis(2,4,6-trimethylphenylimidazolin)-2-ylidene]} and 6a-d {NHC=SIPr [1,3-bis(2,6-diisopropylphenylimidazolin)-2-ylidene]} in 66-84% yield. The lower steric bulk and the decreased donation of the diaryl ether oxygen atoms in complexes 5 and 6 led to rapidly initiating precatalysts. The Ru(II/III) redox potentials of complexes 6 were determined (6a-d: ΔE=0.89-1.08 V). In the crystal structure of 5b two independent molecules were observed in the unit cell, displaying Ru-O distances of 226.6(4) and 230.5(3) pm. The catalytic performance of complexes 5 and 6 in various ring-closing metathesis (RCM) reactions was studied. Catalyst loadings of between 15-200 ppm are sufficient for the formation of >90% yield of the respective cyclic products. Complex 6b catalyzes the formation of N-protected 2,5-dihydropyrroles with up to TON 64,000 and TOF 256,000 h-1, of the N-protected 1,2,3,6- tetrahydropyridines with up to TON 18,200 and TOF 73,000 h-1 and of the N-protected 2,3,6,7-tetrahydroazepines with up to TON 8,100 and TOF 32,000 h-1 with yields ranging between 77 and 96%.
Fast olefin metathesis at low catalyst loading
Peeck, Lars H.,Savka, Roman D.,Plenio, Herbert
, p. 12845 - 12853 (2012/11/06)
Reactions of the Grubbs 3rd generation complexes [RuCl2(NHC) (Ind)(Py)] (N-heterocyclic carbene (NHC)=1,3-bis(2,4,6- trimethylphenylimidazolin)-2-ylidene (SIMes), 1,3-bis(2,6- diisopropylphenylimidazolin)-2-ylidene (SIPr), or 1,3-bis(2,6- diisopropylphenylimidazol)-2-ylidene (IPr); Ind=3-phenylindenylid-1-ene, Py=pyridine) with 2-ethenyl-N-alkylaniline (alkyl=Me, Et) result in the formation of the new N-Grubbs-Hoveyda-type complexes 5 (NHC=SIMes, alkyl=Me), 6 (SIMes, Et), 7 (IPr, Me), 8 (SIPr, Me), and 9 (SIPr, Et) with N-chelating benzylidene ligands in yields of 50-75 %. Compared to their respective, conventional, O-Grubbs-Hoveyda complexes, the new complexes are characterized by fast catalyst activation, which translates into fast and efficient ring-closing metathesis (RCM) reactivity. Catalyst loadings of 15-150 ppm (0.0015-0.015 mol %) are sufficient for the conversion of a wide range of diolefinic substrates into the respective RCM products after 15 min at 50 °C in toluene; compounds 8 and 9 are the most catalytically active complexes. The use of complex 8 in RCM reactions enables the formation of N-protected 2,5-dihydropyrroles with turnover numbers (TONs) of up to 58 000 and turnover frequencies (TOFs) of up to 232 000 h-1; the use of the N-protected 1,2,3,6-tetrahydropyridines proceeds with TONs of up to 37 000 and TOFs of up to 147 000 h-1; and the use of the N-protected 2,3,6,7-tetrahydroazepines proceeds with TONs of up to 19 000 and TOFs of up to 76 000 h-1, with yields for these reactions ranging from 83-92 %. The tortoise and the hare: The use of diphenylalkylamino-based instead of phenyldialkylamino-based styrenes (see figure) leads to rapidly initiating precatalysts that enable very fast ring-closing metathesis reactions with turnover numbers of up to 58 000 and turnover frequencies of up to 232 000 h-1. Copyright
Synthesis of pentabromopseudilin and other arylpyrrole derivatives via Heck arylations
Schwalm, Cristiane S.,De Castro, Ilton B.D.,Ferrari, Jailton,De Oliveira, Fábio L.,Aparicio, Ricardo,Correia, Carlos Roque D.
supporting information; experimental part, p. 1660 - 1663 (2012/04/10)
Pentrabromopseudilin and other 2 and 3-arylpyrrole derivatives were synthesized through the Heck-Matsuda reaction involving endocyclic enecarbamates and N-protected 3-pyrrolines, respectively. The overall processes permitted an easy and efficient access t
How important is the release-return mechanism in olefin metathesis?
Vorfalt, Tim,Wannowius, Klaus J.,Thiel, Vasco,Plenio, Herbert
supporting information; experimental part, p. 12312 - 12315 (2011/02/16)
From whose bourns no traveller returns, puzzles the will: UV/Vis, 19F NMR, and fluorescence spectroscopic studies (see graphic) provide no evidence supporting the boomerang mechanism in Grubbs-Hoveyda complexes, which is the return of the isopropoxy styrene as a benzylidene ether ligand following its release during catalyst initiation.
Batchwise and continuous organophilic nanofiltration of Grubbs-type olefin metathesis catalysts
Schoeps, Dirk,Buhr, Kristian,Dijkstra, Marga,Ebert, Katrin,Plenio, Herbert
experimental part, p. 2960 - 2965 (2009/12/08)
A mass-tagged N-mesityl imidazolinium salt with four additional -CH 2NCy2 substituents was synthesized, leading to a molecular mass of nearly 1100 g mol-1 in the corresponding carbene ligand. This mass-tagged ligand was used to generate the respective Grubbs II and Grubbs-Hoveyda type complexes. The catalytic activity of the latter complex was tested in several olefin metathesis reactions and found to be slightly superior to that of the related N-mesityl based complex. In batchwise solvent resistant nanofiltration experiments the ruthenium complex dissolved in toluene and following a metathesis reactions was efficiently retained (>99.8%) by a single nanofiltration; the permeate contained less than 4 ppm of Ru. Equally efficient catalyst retention was observed in a membrane reactor utilized for the continuous synthesis of a RCM product.
Synthesis of Piperazines and Thiomorpholines by Ozonolysis of Cyclic Olefins and Reductive N-Alkylation
Kawaguchi, Mamoru,Hayashi, Osamu,Kanamoto, Masahiro,Hamada, Masayuki,Yamamoto, Yukio,Oda, Jun'ichi
, p. 435 - 440 (2007/10/02)
Ozonized 1-trifluoroacetyl-3-pyrroline (2a) and 3-sulfolene (6) were reduced with sodium cyanoborohydride (1) to afford the dialdehyde, which reacted in situ with the primary amines 3ad in the presence of 1 to give the piperazines 4ad (2160 percent) and the dioxothiomorpholines 7ad (2676 percent).Reduction of 7a and 7c with diisobutylaluminum hydride yielded the thiomorpholines 8a and 8c, respectively.On the other hand, the 9-membered azacrown ethers 10 and 11 were obtained when N,N'-dibenzylethylenediamine (9) was employed.The dioxothiomorpholine derivatives 13 of amino acids were also prepared by the same treatment.
