On the mechanism of oxygen-atom or nitrene-group transfer in reactions of epoxides and aziridines with tungsten(II) compounds
摘要:
The tungsten(II) complexes WCl2(PMePh2)4 (1) and WCl2(CH2=CH2)2(PMePh2)2 (2) react with epoxides and aziridines to form tungsten(IV)-oxo and -imido complexes. The relative reactivities of epoxides with 2 have been determined from competition experiments. More substituted epoxides are harder to deoxygenate: the reactivities of ethylene, isobutylene, and tetramethylethylene oxides fall in the geometric progression 100:10:1. cis-2-Butene oxide is deoxygenated faster than its trans isomer. Reaction occurs with predominant (greater-than-or-equal-to 85%) retention of configuration (e.g. cis epoxides to cis olefins). The reaction of 2 with ethylene-d4 oxide yields W(O)Cl2(CH2=CH2)(PMePh2)2 (4) and uncoordinated CD2=CD2. The data suggest that de-epoxidation occurs via oxygen atom abstraction, and not via an oxametallacyclobutane which rearranges to an oxo-ethylene complex. Similarly, the tungsten center is suggested to attack the nitrogen atom of the aziridines, rather than react by initial oxidative addition of a C-N bond. This is indicated by the observation of an N-bound complex of aziridine and by the much slower rates of reaction for aziridines with bulky substituents on the nitrogen. The reactivities of para-substituted styrene epoxides are not strongly affected by the nature of the substituent (a-rho+-value of -0.5 is calculated with Hammett sigma+ parameters) indicating that the transition state is not very polar, although there appears to be some conjugation between the phenyl ring' and the epoxide. In sum, the data are most consistent with either concerted oxygen or nitrene transfer to tungsten or a mechanism involving a short-lived radical intermediate.
[DE] SÄUREGRUPPEN-SUBSTITUIERTE DIPHENYLAZETIDINONE, VERFAHREN ZU DEREN HERSTELLUNG, DIESE VERBINDUNGEN ENTHALTENDE ARZNEIMITTEL UND DEREN VERWENDUNG<br/>[EN] DIPHENYL AZETIDINONES SUBSTITUTED BY ACIDIC GROUPS, METHOD FOR THEIR PRODUCTION, MEDICAMENTS CONTAINING SAID COMPOUNDS AND USE THEREOF<br/>[FR] DIPHENYLAZETINIDONES SUBSTITUEES PAR DES GROUPES ACIDES, PROCEDE DE FABRICATION, MEDICAMENTS CONTENANT CES COMPOSES ET UTILISATION DE CES MEDICAMENTS
申请人:AVENTIS PHARMA GMBH
公开号:WO2004000805A1
公开(公告)日:2003-12-31
Die Erfindung betrifft Verbindungen der Formel (I), worin R1, R2, R3, R4, R5 , and R6 die angegebenen Bedeutungen haben, sowie deren physiologisch verträgliche Salze. Die Verbindungen eignen sich z.B. als Hypolipidämika.
Anion polarity-induced dual oxidation states in a dual-layered purely organic paramagnetic charge-transfer salt, (TTF)3(PO-CON(CH3)C2H4SO3)2, where PO = 2,2,5,5-tetramethyl-3-pyrrolin-1-oxyl free radical
作者:Hiroki Akutsu、Atsushi Kawamura、Jun-ichi Yamada、Shin'ichi Nakatsuji、Scott S. Turner
DOI:10.1039/c1ce05578j
日期:——
The purely organic paramagnetic charge-transfer salt (TTF)3(PO-CON(CH3)C2H4SO3)2 was prepared. The anisotropic anion forms a head-to-head arrangement in the anionic layer, giving dual donor layers with different oxidation states. SQUID magnetometry indicates that spins are localized not only on the free radical (PO) but also on both TTF layers.
The incorporation and extension of synthetically unprecedented nucleoside phosphoramidate sulfonates is demonstrated using thermophilic and mesophilic microbial polymerases.
使用嗜热和中温微生物聚合酶展示了合成前所未有的核苷酸磷酸酰胺磺酸盐的合并和扩展。
Synthesis of Conjugates of Lupane-Type Pentacyclic Triterpenoids with 2-Aminoethane- and N-Methyl-2-Aminoethanesulfonic Acids. Assessment of in vitro Toxicity
作者:N. G. Komissarova、S. N. Dubovitskii、O. V. Shitikova、E. M. Vyrypaev、L. V. Spirikhin、E. M. Eropkina、T. G. Lobova、M. Yu. Eropkin、M. S. Yunusov
DOI:10.1007/s10600-017-2153-6
日期:2017.9
Conjugates of betulin and betulinic and betulonic acids with 2-aminoethane- and N-methyl-2-aminoethanesulfonic acids were synthesized for the first time and were interesting as potential biologically active compounds. Experiments in vitro in MDCK cell culture using the MTT assay found that betulin and betulinic-acid derivatives with aminoethanesulfonic acid bound to triterpene C-3 or C-28 through an ester linker were less toxic than the native compounds.