55424-48-1Relevant academic research and scientific papers
Basicities and Nucleophilicities of Pyrrolidines and Imidazolidinones Used as Organocatalysts
An, Feng,Maji, Biplab,Min, Elizabeth,Ofial, Armin R.,Mayr, Herbert
supporting information, p. 1526 - 1547 (2020/02/04)
The Br?nsted basicities pKaH (i.e., pKa of the conjugate acids) of 32 pyrrolidines and imidazolidinones, commonly used in organocatalytic reactions, have been determined photometrically in acetonitrile solution using CH acids as indicators. Most investigated pyrrolidines have basicities in the range 16 aH aH aH 12.6) and the 2-imidazoliummethyl-substituted pyrrolidine A21 (pKaH 11.1) are outside the typical range for pyrrolidines with basicities comparable to those of imidazolidinones. Kinetics of the reactions of these 32 organocatalysts with benzhydrylium ions (Ar2CH+) and structurally related quinone methides, common reference electrophiles for quantifying nucleophilic reactivities, have been measured photometrically. Most reactions followed second-order kinetics, first order in amine and first order in electrophile. More complex kinetics were observed for the reactions of imidazolidinones and several pyrrolidines carrying bulky 2-substituents, due to reversibility of the initial attack of the amines at the electrophiles followed by rate-determining deprotonation of the intermediate ammonium ions. In the presence of 2,4,6-collidine or 2,6-di-tert-butyl-4-methyl-pyridine, the deprotonation of the initial adducts became faster, which allowed the rate of the attack of the amines at the electrophiles to be determined. The resulting second-order rate constants k2 followed the correlation log?k2(20 °C) = sN(N + E), where electrophiles are characterized by one parameter (E) and nucleophiles are characterized by the two solvent-dependent parameters N and sN. In this way, the organocatalysts A1-A32 were integrated in our comprehensive nucleophilicity scale, which compares n-, -, and σ-nucleophiles. The nucleophilic reactivities of the title compounds correlate only poorly with their Br?nsted basicities.
Enantioselective copper-catalyzed 1,4-addition of dialkylzincs to enones followed by trapping with allyl iodide derivatives
Kawamura, Kenjiro,Fukuzawa, Hitomi,Hayashi, Masahiko
scheme or table, p. 640 - 647 (2011/08/06)
Enantioselective copper-catalyzed 1,4-addition of dialkylzincs to enones proceeded in the presence of 0.1 mol% of Cu(OTf)2 and 0.25 mol% of an N,N,P-ligand containing a quinoline moiety to afford the corresponding conjugated adducts in 99%ee. The intermediate zinc enolates were trapped with substituted allyl iodides to give disubstituted ketones with high diastereoselectivity and enantioselectivity.
Enantioselective intramolecular Rauhut-Currier reaction catalyzed by chiral phosphinothiourea
Gong, Jing-Jing,Li, Tian-Ze,Pan, Kun,Wu, Xin-Yan
supporting information; experimental part, p. 1491 - 1493 (2011/03/22)
Chiral organophosphine-catalyzed enantioselective Rauhut-Currier reaction has been disclosed for the first time. With l-valine-derived phosphinothiourea, the intramolecular Rauhut-Currier reaction of bis(enones) was achieved in good yields (up to 99%) wit
Stereoselective synthesis of 2,4,5-trisubstituted piperidines via radical cyclization
Ragoussi, Maria-Eleni,Walker, Stephen M.,Piccanello, Andrea,Kariuki, Benson M.,Horton, Peter N.,Spencer, Neil,Snaith, John S.
scheme or table, p. 7347 - 7357 (2011/02/16)
A novel approach to 2,4,5-trisubstituted piperidines is reported, involving the 6-exo cyclization of stabilized radicals onto α,β-unsaturated esters. Only two of the four possible diastereoisomers are observed, with diastereomeric ratios ranging from 3:2
Synthesis and biological evaluation of reversible inhibitors of IdeS, a bacterial cysteine protease and virulence determinant
Berggren, Kristina,Johansson, Bjoern,Fex, Tomas,Kihlberg, Jan,Bjoerck, Lars,Luthman, Kristina
experimental part, p. 3463 - 3470 (2009/09/25)
Analogues of the irreversible protease inhibitors TPCK and TLCK have been synthesized and tested as inhibitors of the bacterial cysteine protease IdeS excreted by Streptococcus pyogenes. Eight compounds were identified as inhibitors of IdeS in an in vitro
Novel N,N,P-tridentate ligands for the highly enantioselective copper-catalyzed 1,4-addition of dialkylzincs to enones
Kawamura, Kenjiro,Fukuzawa, Hitomi,Hayashi, Masahiko
supporting information; experimental part, p. 3509 - 3512 (2009/05/07)
(Chemical Equation Presented) Use of 0.25 mol % of the N,N,P-tridentate ligand containing the 2-quinolyl moiety (1 and 2) and 0.1 mol % of Cu(OTf) 2 enabled the enantioselective 1,4-addition of dialkylzincs to cyclic enones to produce 1,4-adduc
Stereoselective synthesis of 2,4,5-trisubstituted piperidines by carbonyl ene and Prins cyclisations
Cariou, Claire A.M.,Kariuki, Benson M.,Snaith, John S.
supporting information; experimental part, p. 3337 - 3348 (2009/02/05)
An approach to 2,4,5-trisubstituted piperidines is reported, in which the key step is the Prins or carbonyl ene cyclisation of aldehydes of the type 1. Prins cyclisation catalysed by concentrated hydrochloric acid in CH 2Cl2 at -78 °C afforded good yields of two of the four possible diastereomeric piperidines, with the 4,5-cis product 7 predominating in a diastereomeric ratio of up to 94: 6. The diastereoselectivity of the cyclisation decreased as the 2-substituent increased in size, becoming unselective for very bulky 2-substituents. In contrast, cyclisation catalysed by MeAlCl2 in CH2Cl2 or CHCl3 at temperatures of between 20-60 °C, favoured the 4,5-trans diastereomer 8, in a diastereomeric ratio of up to 99: 1. The low-temperature cyclisations catalysed by HCl proceed under kinetic control via a mechanism involving the development of significant carbocationic character, in which the 4,5-cis cation is more stable than the 4,5-trans cation as a result of overlap with the neighbouring oxygen. The cyclisations catalysed by MeAlCl2 proceed under thermodynamic control, affording the product in which both the 4- and 5-substituents are equatorial.
Stereoselective synthesis of 2,4,5-trisubstituted piperidines by carbonyl ene and Prins cyclisations
Cariou, Claire A. M.,Snaith, John S.
, p. 51 - 53 (2007/10/03)
Intramolecular carbonyl ene reactions present a method for ring closure, leading to the formation of two contiguous stereocentres with an often high degree of stereocontrol. The extension of this approach to the synthesis of 2,4,5-trisubstituted piperidin
The synthesis of chiral annulet 1,4,7-triazacyclononanes
Argouarch, Gilles,Gibson, Colin L,Stones, Graham,Sherrington, David C
, p. 3795 - 3798 (2007/10/03)
Novel and flexible routes for the synthesis of chiral ring annulet 2,6-disubstituted 1,4,7-trimethyl-1,4,7-triazamacrocycles are described. Efficient macrocyclisations were realised provided that chiral analogues of N,N-bis-[2-(toluene-sulfonylamino)ethyl]-toluene-4-sulfonamide were used as the nucleophilic components. Complexes prepared, in situ, from these 2,6-disubstituted 1,4,7-trimethyl-1,4,7-triazamacrocycles and manganese(II) catalysed the asymmetric epoxidation of styrene with hydrogen peroxide.
Asymmetric Reduction of Chiral Acetophenone Oxime Ethers to Optically Active Primary Amines
Itsuno, Shinichi,Tanaka, Kazuo,Ito, Koichi
, p. 1133 - 1136 (2007/10/02)
Chiral oxime ethers were synthesized from Na salt of acetophenone oxime and chiral halides, tosylates, or N-tosylaziridines which were derived from β-pinene or α-amino acids.Asymmetric reduction of the chiral oxime ether with LiAlH4 or BH3*THF gave the optically active primary amine.
