Beiträge zur chemie der Pyrrolpigmente, 10. Mitt.: Elektronenspektrometrische Untersuchungen über die Struktur von Quadratsäurederivaten

The structure of squaric acid derivatives was investigated on the basis of the PPP—SCF—LCAO—MO—CI method utilizing the π-electron densities and bond orders. The parameters used in the calculations were modified to fit the experimental data for representative compounds. The data were obtained by X-ray photoelectron spectrometry and electron absorption spectroscopy (including the polarization of the bands as determined by liquid crystal induced circular dichroism measurements).     

On the synthesis and chiroptical properties of the tri- and tetragalloylquinic acids

Summary A synthesis of the potential pharmaceutical agents 3,4,5-trigalloylquinic acid and 1,3,4,5-tetragalloylquinic acid is described. It involves three steps starting from commercially available quinic acid and provides overall yields of about 15%. The acylation of benzyl or 4-nitrobenzyl quinate with tribenzylgalloyl chloride is the key step. It leads selectively to the triacyl product in the case of benzyl quinate and can be either stopped at the triacyl stage or driven to the tetraacyl derivative in the case of the 4-nitrobenzyl quinate. From the chiroptical properties of the two compounds their stereochemistry was derived by means of the benzoate rule.

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Zu Synthese und chiroptischen Eigenschaften der Tri- und Tetragalloylchinasäuren

Zusammenfassung Eine Synthese von 3,4,5-Trigalloylchinasäure und 1,3,4,5-Tetragalloylchinasäure. die potentielle Pharmaka darstellen, wird beschrieben. Sie umfaßt drei Stufen, welche ausgehend von kommerziell erhältlicher Chinasäure Gesamtausbeuten um 15% ergeben. Die entscheidende Stufe dabei ist die Acylierung von Benzyl- oder 4-Nitrobenzylchinat mit Tribenzylgalloylchlorid. Sie führt im Falle des Benzylchinats selektiv zum Triacylprodukt und kann im Fall des 4-Nitrobenzylchinats entweder auf der Stufe des Triacylderivates abgebrochen oder bis zum Tetraacylprodukt durchgezogen werden. Aus den chiroptischen Eigenschaften der beiden Verbindungen wurde ihre Stereochemie abgeleitet.

     

Neue Phellandren-Derivate aus dem Wurzelöl von Angelica archangelicaL

New Phellandrene Derivatives from the Root Oil of Angelica archangelica L . 2-Nitro-1,5-p-menthadiene ( 5 ), trans- and cis-6-nitro-1(7), 2-p-menthadiene ( 6 and 7 ), trans-1(7), 5-p-menthadien-2-yl acetate ( 9 ) and a formal phellandrene derivative, 7-isopropyl-5-methyl-5-bicyclo [2.2.2]octen-2-one ( 16 ), have been identified in the root oil of Angelica archangelica L . Starting from (?)-(R)-α-phellandrene ( 1 ) (R)- 5 , (4R, 6S)- 6 /(4R, 6R)- 7 , (2S, 4R)- 9 and (1R, 4R, 7R)- 16 as well as (2S, 4R)- 11 , (2R, 4R)- 12 and (2R, 4R)- 10 have been prepared.     

Quadratically constrained least squares and quadratic problems

Summary We consider the following problem: Compute a vectorx such that Ax–b₂=min, subject to the constraint x₂=. A new approach to this problem based on Gauss quadrature is given. The method is especially well suited when the dimensions ofA are large and the matrix is sparse.It is also possible to extend this technique to a constrained quadratic form: For a symmetric matrixA we consider the minimization ofx ^T A x–2b ^T x subject to the constraint x₂=.Some numerical examples are given.This work was in part supported by the National Science Foundation under Grant DCR-8412314 and by the National Institute of Standards and Technology under Grant 60NANB9D0908.     

A Theoretical Study of Complex Formation between Formaldehyde and Lithium

Ab initio SCF and CI calculations on the cationic and neutral complexes of formaldehyde and lithium are reported. For the cationic complex CH₂O/Li⁺, the stabilization energy of 41.7 kcal/mol obtained from the SCF calculation increases to 51.6 kcal/mol if a configuration interaction is introduced. For the neutral complex CH₂O^?/Li⁺, the C_2v-conformer of the ²A₁-state with the equilibrium bond distances of d(C? O) = 1.23 Å and d (O? Li) = 1.90 Å is calculated to be more stable than the ₂B₁-state with d (C? O) = 1.34 Å, and d (O? Li) = 1.65 Å. Charge transfer and polarization effects upon complex formation are discussed.     

Chemistry of (Carbonyl)(nitrosyl)[bis(phosphorus donor)]rhenium Complexes

The chemistry of [Re(CO)(NO)L₂] fragments (L ? phosphorus donor) was explored. Starting from [Re(CO)₅Cl] the synthesis of [Re₂Cl₂(μ-Cl)₂(CO)₄(NO)₂] ( 1 ) was accomplished via the preparation of [Et₄N]₂[Re₂Cl₂(μ-Cl)₂(CO)₆] and nitrosylation of this compound with [NO][BF₄]. Complex 1 was converted to [RecL₂(CO)(NO)L₂] complexes 2 ( a L = (MeO)₃P; b L = (EtO)₃P; c L = (i-PrO)₃P; d L ? Me₃P; e L ? Et₃P; f L ? Cy₃P) by heating with L in MeCN. In the case of the reaction of L = (MeO)₃P, a trisubstitued compound mer-{ReCl₂(NO)[P(OMe)₃]₃} 3 was also obtained. Replacement of the Cl ligands in 2a–e with Me groups was achieved by reacting them with MeLi in Et₂O yielding cis, trans-[Re(CO)(NO)Me₂L₂]complexes 4a–e . Reaction of 2a–e with Li[BHEt₃] led to substitution of one Cl by an H ligand with formation of [ReCl(CO)H(NO)L₂] compounds 5a–;e , displaying trans-H,NO geometries. The hydride-transfer agent Na[AlH₂(OCH₂CH₂OCH₃)₂] transformed 2 into the cis-dihydride systems [Re(CO)H₂(NO)L₂] 6a–f . Reductive carbonylation of 2a–d in the presence of Na/Hg and CO gave pentacoordinate [Re(CO)₂(NO)L₂] complexes 7b–d , and under comparable conditions the Cl substituents of 2b–f were replaced by tolane using Mg or t-BuLi giving trigonal bipyramidal [Re(CO)(NO)L₂(PhC?CPh)] compounds 8b–f . Complexes 5c , 6a , and 8d were characterized by X-ray crystal-structure analysis.     

Anionic Graft Copolymers. ll. Styrene Grafts on EPT Rubbers

Rubbers containing a low level of unsaturation such as EPT may be metalated with a chelate made from s-butyllithium and N,N,N′- N′ -tetramethylethylethylenediamine. The lithiated polymers, reacted with styrene, result in polystyrene graft copolymers. The physical properties are affected by graft level and polystyrene content.     

Comprehensive Characterization of Shredded Lithium-Ion Battery Recycling Material

Herein we report on an analytical study of dry-shredded lithium-ion battery (LIB) materials with unknown composition. Samples from an industrial recycling process were analyzed concerning the elemental composition and (organic) compound speciation. Deep understanding of the base material for LIB recycling was obtained by identification and analysis of transition metal stoichiometry, current collector metals, base electrolyte and electrolyte additive residues, aging marker molecules and polymer binder fingerprints. For reversed engineering purposes, the main electrode and electrolyte chemistries were traced back to pristine materials. Furthermore, possible lifetime application and accompanied aging was evaluated based on target analysis on characteristic molecules described in literature. With this, the reported analytics provided precious information for value estimation of the undefined spent batteries and enabled tailored recycling process deliberations. The comprehensive feedstock characterization shown in this work paves the way for targeted process control in LIB recycling processes.