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991.
Lauren E. Longobardi Dr. Timothy C. Johnstone Rosalyn L. Falconer Dr. Christopher A. Russell Prof. Dr. Douglas W. Stephan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(36):12665-12669
The hydroboration of phosphaalkynes with Piers’ borane (HB(C6F5)2) generated unusual phosphaalkenylboranes [RCH=PB(C6F5)2]2 that persisted as dimers in both solution and the solid state. These P2B2 heterocycles underwent ring opening when subjected to nucleophiles, such as pyridine and tert‐butylisocyanide, to yield monomeric phosphaalkenylborane adducts RCH=PB(C6F5)2(L). DFT calculations were performed to probe the nature of the interaction of phosphaalkynes with boranes. 相似文献
992.
Total Synthesis of Δ12‐Prostaglandin J3: Evolution of Synthetic Strategies to a Streamlined Process 下载免费PDF全文
Prof. Dr. K. C. Nicolaou Dr. Kiran Kumar Pulukuri Ruocheng Yu Dr. Stephan Rigol Dr. Philipp Heretsch Dr. Charles I. Grove Christopher R. H. Hale Dr. Abdelatif ElMarrouni 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(25):8559-8570
The total synthesis of Δ12‐prostaglandin J3 (Δ12‐PGJ3, 1 ), a reported leukemia stem cell ablator, through a number of strategies and tactics is described. The signature cross‐conjugated dienone structural motif of 1 was forged by an aldol reaction/dehydration sequence from key building blocks enone 13 and aldehyde 14 , whose lone stereocenters were generated by an asymmetric Tsuji–Trost reaction and an asymmetric Mukaiyama aldol reaction, respectively. During this program, a substituent‐governed regioselectivity pattern for the Rh‐catalyzed C?H functionalization of cyclopentenes and related olefins was discovered. The evolution of the synthesis of 1 from the original strategy to the final streamlined process proceeded through improvements in the construction of both fragments 13 and 14 , exploration of the chemistry of the hitherto underutilized chiral lactone synthon 57 , and a diastereoselective alkylation of a cyclopentenone intermediate. The described chemistry sets the stage for large‐scale production of Δ12‐PGJ3 and designed analogues for further biological and pharmacological studies. 相似文献
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Dempe Stephan Dinh Nguyen Dutta Joydeep Pandit Tanushree 《Mathematical Programming》2021,188(1):227-253
Mathematical Programming - In this paper we discuss the simple bilevel programming problem (SBP) and its extension, the simple mathematical programming problem under equilibrium constraints... 相似文献
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We study the problem of inhomogeneous diophantine approximation under certain primality restrictions. 相似文献
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Dr. Jan-Philipp Venne Dr. Bastian Feldscher Dr. Stephan Walleck Anja Stammler Dr. Hartmut Bögge Prof. Dr. Jürgen Schnack Prof. Dr. Thorsten Glaser 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(19):4992-5004
The anisotropy barrier of polynuclear single-molecule magnets is expected to be higher with less tunneling the better stabilized the spin ground state is so that less MS mixing in the ground state and with excited spin states occur. We have realized this experimentally in two structurally related heptanuclear SMMs: the triplesalen-based [MnIII 6 CrIII]3+ and the triplesalalen-based *[MnIII 6 CrIII]3+ . The ligand system triplesalen was developed to enforce ferromagnetic interactions by the spin-polarization mechanism. However, we found weak antiferromagnetic couplings, that we assigned to an inefficient spin-polarization by a heteroradialene formation. To prevent this heteroradialene formation, the triplesalalen ligand H6talalen was designed. Here, we present the building block [(talalen )MnIII3]3+ and its application for the assembly of [{(talalen )MnIII3}2{CrIII(CN)6}]3+ (= *[MnIII 6 CrIII]3+ ). Both the trinuclear and heptanuclear complexes are SMMs. The comparison to the related triplesalen complex [(feld )MnIII3]3+ proves the absence of heteroradialene character and the enforcement of ferromagnetic MnIII-MnIII interactions in the (talalen )6− complexes. This results in an increase of the barrier for spin reversal Ueff from 25 K in the triplesalen-based [MnIII 6 CrIII]3+ SMMs to 37 K in the triplesalalen-based *[MnIII 6 CrIII]3+ SMM proving the success of our concept. Based on this study, the next step in the rational improvement of our SMMs is discussed. 相似文献