- Exploring steric effects in diastereoselective synthesis of chiral aminophenolate zinc complexes and stereoselective ring-opening polymerization of rac-lactide
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A series of tridentate chiral aminophenol proligands and corresponding zinc complexes, LZnX (L = (S)-2-{[(1-R4-2-pyrrolidinyl)CH2N(R3)-]CH2}-6-R1-4-R2-C6H2O, X = N(SiMe3)2, R3 = nBu, R4 = Bn: R1 = R2 = Cl (1), R1 = R2 = Me (2), R1 = R2 = tBu (3); X = N(SiMe3)2, R1 = trityl, R2 = Me: R3 = n-octyl, R4 = Bn (4), R3 = Bn, R4 = Bn (5), R3 = nBu, R4 = naphthalen-1-ylmethyl (6), R3 = nBu, R4 = iPr (7); R1 = R2 = cumyl, R3 = Et, R4 = Bn: X = N(SiMe3)2 (8), X = OtBu (9), X = Et (10), X = Cl (11)), have been synthesized. Complexes 4, 6, and 11 were obtained as enantiopure products (4 and 6 as enantiopure a; 11 as enantiopure b), while complexes 1-3, 5, and 7-10 as a pair of diastereomers, but in different ratios, which have been proved by X-ray diffraction and NMR spectroscopic studies. When exposed to the ring-opening polymerization of rac-lactide, most of these complexes can effectively produce PLAs with narrow polydispersities, desirable molecular weights, and moderate to high isotacticities. The structure-selectivity relationships, including the relationships of structure-synthesis diastereoselectivity and structure-polymerization stereoselectivity, have been further investigated. Consistent trends of diastereoselectivity and stereoselectivity are observed with the variations of the R1 group at the ortho-position of the phenolate ring and the R3 group in the pyrrolidinyl moiety. The decrease of the steric bulkiness of the R4 group on the central amine has less influence on the diastereoselectivity, but leads to considerable loss of the stereoselectivity, whereas the decrease of the steric bulkiness of the X group results in a reverse of the diastereoselectivity, but shows no influence on the stereoselectivity. There is probably no direct relationship between the diastereoselectivity in complex synthesis and the stereoselectivity of the complex toward the ROP of rac-LA. The stereocontrol of these complexes might largely rely on the substituents in the ligand framework rather than their diastereomer ratios.
- Wang, Haobing,Yang, Yang,Ma, Haiyan
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supporting information
p. 7356 - 7372
(2016/08/06)
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- Highly diastereoselective synthesis of chiral aminophenolate zinc complexes and isoselective polymerization of rac-lactide
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An enantiopure zinc complex supported by an aminophenolate ligand with multiple stereogenic centers has been diastereoselectively synthesized via the variation of the ortho-substituent of a phenoxy moiety and the N-alkyl group of a chiral pyrrolidinyl ring in the ligand framework, which displays high isoselectivity in the polymerization of rac-lactide.
- Wang, Haobing,Ma, Haiyan
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supporting information
p. 8686 - 8688
(2013/09/23)
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- COMPOUNDS USEFUL AS INHIBITORS OF ATR KINASE
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The present disclosure relates to pyrazine compounds of formula (I) wherein L, n, R1, and R2 are as described in the specification. These compounds are useful as inhibitors of ATR protein kinase. The disclosure also relates to pharmaceutically acceptable compositions comprising the compounds of the disclosure; methods of treating of various diseases, disorders, and conditions using the compounds of the disclosure; processes for preparing the compounds of the disclosure; intermediates for the preparation of the compounds of the disclosure; and methods of using the compounds in in vitro applications, such as the study of kinases in biological and pathological phenomena; the study of intracellular signal transduction pathways mediated by such kinases; and the comparative evaluation of new kinase inhibitors.
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Page/Page column 190
(2010/06/11)
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- EFFICIENT STEREOCONSERVATIVE SYNTHESIS OF 1-SUBSTITUTED (S)- AND (R)-2-AMINOMETHYLPYRROLIDINES AND INTERMEDIATES THERETO
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Stereoconservative method for preparation of an (R)- or (S)-isomer of the compound of the formula I with at least 95% optical purity wherein R1 is a hydrogen atom, a saturated or unsaturated lower alkyl group, a cycloalkyl group, or a group (CH2)m Ph wherein m is 0-3 and Ph is a substituted or unsubstituted phenyl group including 1) O,N-dialkylation, directly or stepwise of (R)- or (S)-proline 2) aminolysis 3) reduction to formation of the (R)- or (S)-isomer of the compound of the formula I, and new intermediates II and III in optical active form obtained by the reaction steps above and wherein R2 is defined as R1 above.
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- N-Fluoroalkylated and N-Alkylated Analogues of the Dopaminergic D-2 Receptor Antagonist Raclopride
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A series of raclopride -1-ethylpyrrolidine> derivatives bearing pyrrolidino N-fluoroalkyl or -alkyl substituents were synthesized and evaluated as potential dopaminergic receptor-based positron tom
- Lannoye, G. S.,Moerlein, S. M.,Parkinson, D.,Welch, M. J.
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p. 2430 - 2437
(2007/10/02)
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- Efficient Stereoconservative Syntheses of 1-Substituted (S)- and (R)-2-Aminomethylpyrrolidines
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Three-step stereoconservative syntheses of chiral 1-substituted 2-aminomethylpyrrolidines with high optical purities from D- or L-proline are described.The key intermediates, 1-substituted prolinamides, were obtained by N,O-dialkylation of proline followed by ammonolysis or by 1-alkylation of prolinamide.Reduction furnished the optically pure (about 99percent e.e.) pyrrolidine derivatives, which are useful as intermediates in the preparation of antipsychotic substituted benzamides.
- Hoegberg, Thomas,Raemsby, Sten,Stroem, Peter
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p. 660 - 664
(2007/10/02)
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- Cyanide as an Efficient and Mild Catalyst in the Aminolysis of Esters
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Cyanide anion was found to be a versatile catalyst in the aminolysis of nonactivated esters.A comparative study on various catalysts, including (dimethylamino)pyridine, 2-hydroxypyridine, imidazole, and sodium cyanide, in the ammonolysis of ethyl (S)-1-ethyl-2-pyrrolidinecarboxylate (1) in methanol showed sodium cyanide to be the superior catalyst.Furthermore, the reaction was completely stereoconservative; i.e., less than 1percent racemization occurred.Cyanide ion also proved to be an efficient catalyst in the transesterification with the solvent.Comparative studies on 1, ethyl benzoate (4), ethyl 3-phenylpropionate (5), and ethyl phenoxyacetate (6) in aminolysis with ammonia, methylamine, and dimethylamine in methanol showed cyanide to be a general catalyst.The reactivity order for various esters was found to be MeNH2 > NH3 > Me2NH.
- Hoegberg, Thomas,Stroem, Peter,Ebner, Michael,Raemsby, Sten
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p. 2033 - 2036
(2007/10/02)
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