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1.
Beyond Stereoselectivity,Switchable Catalysis: Some of the Last Frontier Challenges in Ring‐Opening Polymerization of Cyclic Esters
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Dr. Sophie M. Guillaume Dr. Evgueni Kirillov Dr. Yann Sarazin Prof. Dr. Jean‐François Carpentier 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):7988-8003
Metal‐based catalysts and initiators have played a pivotal role in the ring‐opening polymerization (ROP) of cyclic esters, thanks to their high activity and remarkable ability to control precisely the architectures of the resulting polyesters in terms of molar mass, dispersity, microstructure, or tacticity. Today, after two decades of extensive research, the field is slowly reaching maturity. However, several challenges remain, while original concepts have emerged around new types or new applications of catalysis. This Review is not intended to comprehensively cover all of these aspects. Rather, it provides a personal overview of the very recent progress achieved in some selected, important aspects of ROP catalysis—stereocontrol and switchable catalysis. Hence, the first part addresses the development of new metal‐based catalysts for the isoselective ROP of racemic lactide towards stereoblock copolymers, and the use of syndioselective ROP metal catalysts to control the monomer sequence in copolymers. A second part covers the development of ROP catalysts—primarily metal‐based catalysts, but also organocatalysts—that can be externally regulated by the use of chemical or photo stimuli to switch them between two states with different catalytic abilities. Current challenges and opportunities are highlighted. 相似文献
2.
A forecasting model is developed for the number of daily applications for loans at a financial services telephone call centre. The purpose of the forecasts and the associated prediction intervals is to provide effective staffing policies within the call centre. The model building process is constrained by the availability of only 2 years and 7 months of data. The distinctive feature of the data is that demand is driven in the main by advertising. The analysis given focuses on applications stimulated by press advertising. Unlike previous analyses of broadly similar data, where ARIMA models were used, a model with a dynamic level, multiplicative calendar effects and a multiplicative advertising response is developed and shown to be effective. 相似文献
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Stewart C Zieminski A Blessing S Crittenden R Draper P Dzierba A Heinz R Krider J Marshall T Martin J Sambamurti A Smith P Sulanke T Gomez R Dauwe L Haggerty H Malamud E Nikolic M Hagopian S Abrams R Ares J Goldberg H Halliwell C Margulies S McLeod D Salminen A Solomon J Wu G Ellsworth R Goodman J Gupta S Yodh G Watts T Abramov V Antipov Y Baldin B Denisov S Glebov V Gorin Y Kryshkin V Petrukhin A Polovnikov S Sulyaev R 《Physical review D: Particles and fields》1990,42(5):1385-1395
6.
Spoto G Gribov E Bordiga S Lamberti C Ricchiardi G Scarano D Zecchina A 《Chemical communications (Cambridge, England)》2004,(23):2768-2769
Cu(I) ions in Cu-ZSM-5 form Cu+(H2) complexes, stable at room temperature and sub-atmospheric H2 pressure, which do not have any homogeneous analogue except for matrix-isolated [Cu(eta2-H2)Cl]. Comparison with the unstable Na+(H2) adducts formed in the parent Na-ZSM-5 zeolite allow the conclusion that the Cu(I)/H2 bond is governed by sigma-pi overlap forces. 相似文献
7.
Duncan K. Brownsey Ben C. Rowley Evgueni Gorobets Benjamin S. Gelfand Darren J. Derksen 《Chemical science》2021,12(12):4519
Current methods for the preparation of heterobifunctional pomalidomide-conjugates rely on methods that are often low yielding and produce intractable byproducts. Herein we describe our strategy for the reliable and succinct preparation of pomalidomide-linkers which is essential to the formation of these conjugates. We present the preparation of 18 pomalidomide-linkers in high yield compared to current literature methods. Our findings show that secondary amines consistently afford greater yields than their primary counterparts, a trend that we were able to exploit in the synthesis of several new pomalidomide homo-dimers in enhanced yields compared to similar literature syntheses. This trend was further utilised to develop the first one-pot synthesis of JQ1-pomalidomide conjugates in yields up to 62%, providing a method that is suited to rapid preparation of conjugate libraries as is frequently required for the development of new protein degraders.Current methods for the preparation of heterobifunctional pomalidomide-conjugates rely on methods that are often low yielding and produce intractable byproducts. Herein we describe our strategy for the succinct preparation of pomalidomide-linkers. 相似文献
8.
Jesik R Abramov V Antipov Y Baldin B Crittenden R Dauwe L Davis C Denisov S Dyshkant A Dzierba A Glebov V Goldberg H Gribushin A Koreshev V Krider J Krinitsyn A Li R Margulies S Marshall T Martin J Mendez H Petrukhin A Sirotenko V Smith P Solomon J Sulanke T Sulyaev R Vaca F Zieminski A Blusk S Bromberg C Chang P Choudhary B Chung W de Barbaro L Dlugosz W Dunlea J Engels E Fanourakis G Ginther G Hartman K Huston J Kapoor V Lirakis C Lobkowicz F Mani S Mansour J Maul A Miller R Oh B Pothier E 《Physical review letters》1995,74(4):495-498
9.
Abachi S Abbott B Abolins M Acharya BS Adam I Adams DL Adams M Ahn S Aihara H Alvarez G Alves GA Amos N Anderson EW Antipov Y Aronson SH Astur R Avery RE Baden A Balamurali V Balderston J Baldin B Bantly J Bartlett JF Bazizi K Behnke T Bendich J Beri SB Bezzubov V Bhat PC Bhatnagar V Biswas N Blazey G Blessing S Boehnlein A Borcherding F Borders J Bozko N Brandt A Brock R Bross A Buchholz D Burtovoi V Butler JM Callot OH Castilla-Valdez H Chakraborty D Chekulaev S Chen J Chen L Chen W 《Physical review letters》1994,72(14):2138-2142
10.
Rodion V. Panin Nellie R. Khasanova Evgeny V. Antipov Walter Schnelle 《Journal of solid state chemistry》2007,180(5):1566-1574
NaPd3O4, Na2PdO3 and K3Pd2O4 have been prepared by solid-state reaction of Na2O2 or KO2 and PdO in sealed silica tubes. Crystal structures of the synthesized phases were refined by the Rietveld method from X-ray powder diffraction data. NaPd3O4 (space group Pm3¯n, a=5.64979(6) Å, Z=2) is isostructural to NaPt3O4. It consists of NaO8 cubes and PdO4 squares, corner linked into a three-dimensional framework where the planes of neighboring PdO4 squares are perpendicular to each other. Na2PdO3 (space group C2/c, a=5.3857(1) Å, b=9.3297(1) Å, c=10.8136(2) Å, β=99.437(2)°, Z=8) belongs to the Li2RuO3-structure type, being the layered variant of the NaCl structure, where the layers of octahedral interstices filled with Na+ and Pd4+ cations alternate with Na3 layers along the c-axis. Na2PdO3 exhibits a stacking disorder, detected by electron diffraction and Rietveld refinement. K3Pd2O4, prepared for the first time, crystallizes in the orthorhombic space group Cmcm (a=6.1751(6) Å, b=9.1772(12) Å, c=11.3402(12) Å, Z=4). Its structure is composed of planar PdO4 units connected via common edges to form parallel staggered PdO2 strips, where potassium atoms are located between them. Magnetic susceptibility measurements of K3Pd2O4 reveal a Curie-Weiss behavior in the temperature range above 80 K. 相似文献