96343-14-5Relevant academic research and scientific papers
Single-site β-diiminate zinc catalysts for the alternating copolymerization of CO2 and epoxides: Catalyst synthesis and unprecedented polymerization activity
Cheng,Moore,Reczek,Chamberlain,Lobkovsky,Coates
, p. 8738 - 8749 (2007/10/03)
Synthetic routes to zinc β-diiminate complexes are reported. The synthesis of 11 β-diimine [(BDI)-H] ligands, with varying N-aryl substituents and bridging structures, is described. These ligands are converted to (BDI)ZnX complexes (X = OAc, Et, N(SiMe3)2, Br, Cl, OH, OMe, OiPr). X-ray structural data revealed that all zinc complexes examined exist as μ-X-bridged dimers in the solid state, with the exception of the zinc ethyl and amido complexes which were monomeric. Complexes of the form (BDI)ZnOR (R = alkyl, acyl) and (BDI)ZnN(SiMe3)2 are highly active catalysts for the alternating copolymerization of epoxides and CO2. Copolymerizations of cyclohexene oxide (CHO) and CO2 with (BDI-1)ZnX [(BDI-1) = 2-((2,6-diisopropylphenyl)amido)-4-((2,6-diisopropylphenyl)imino)-2-pentene)] and (BDI-2)ZnX [(BDI-2) = 2-((2,6-diethylphenyl-amido)-4-((2,6-diethylphenyl)imino)-2-pentene)], where X = OAc, Et, N(SiMe3)2, Br, Cl, OH, OMe, OiPr, were attempted at 50 °C and 100 psi CO2. Complexes with X = OAc, N(SiMe3)2, OMe, OiPr all produced polycarbonate by the alternated insertion of CHO and CO2 with similar catalytic activities, comparable molecular weights, and narrow molecular weight distributions (MWD ～ 1.1), indicating the copolymerizations are living. Furthermore, ligand effects were shown to dramatically influence the polymerization activity as minor steric changes accelerated or terminated the polymerization activity.
Pyrrolidine-3-carboxylic acids as endothelin antagonists. 4. Side chain conformational restriction leads to ET(B) selectivity
Von Geldern, Thomas W.,Tasker, Andrew S.,Sorensen, Bryan K.,Winn, Martin,Szczepankiewicz, Bruce G.,Dixon, Douglas B.,Chiou, William J.,Wang, Liming,Wessale, Jerry L.,Adler, Andy,Marsh, Kennan C.,Nguyen, Bach,Opgenorth, Terry J.
, p. 3668 - 3678 (2007/10/03)
When the dialkylacetamide side chain of the ETA-selective antagonist ABT-627 is replaced with a 2,6-dialkylacetanilide, the resultant analogues show a complete reversal of receptor selectivity, preferring ETB over ETA. By optimizing the aniline substitution pattern, as well as the alkoxy group on the 2-aryl substituent, it is possible to prepare antagonists with subnanomolar affinity for ETB and with selectivities in excess of 4000-fold. A number of these compounds also show promising pharmacokinetic profiles; a useful balance of properties is found in A-192621 (38). Pharmacology studies with A-192621 serve to reveal the role of the ETB receptor in modulating blood pressure; the observed hypertensive response to persistent ETB blockade is consistent with previous postulates and indicates that ETB-selective antagonists may not be suitable as agents for long-term systemic therapy.
