Lactide Polymerisation with Air‐Stable and Highly Active Zinc Complexes with Guanidine–Pyridine Hybrid Ligands

New class of air‐stable catalysts for lactide polymerisation: Guanidine–pyridine hybrid ligands (picture, left) were used to prepare a series of zinc complexes (e.g., depicted cation [ZnL₂(CF₃SO₃)]⁺, where L is the quinoline‐containing ligand with R¹=R²=R³=R⁴=Me), in which the ligand binds through two different N‐donor atoms. The zinc complexes show high activity in ring‐opening polymerisation of d,l ‐lactide (right), giving polylactide with molecular masses up to 176 000 g mol^?1 and in high yield.

     

Synthesis and MALDI-TOF-MS of PS-PMA and PMA-PS block copolymers

The synthesis of well-defined block copolymers from styrene and methyl acrylate via ATRP is discussed in this contribution. Kinetic studies on these block copolymerizations as well as characterization studies were performed to investigate the monomer composition in the respective PS and PMA blocks. MALDI-TOF-MS was performed to clarify the exact number of repeating units of each block and the total number of units in the block copolymer. Block copolymers up to 22 kDa could be analyzed by MALDI-TOF-MS, whereby polymers with PMA as first block showed a large second distribution corresponding to PMA homopolymers. However, SEC demonstrated that only a small amount of homopolymer was present indicating that care needs to be taken with interpreting MALDI-TOF-MS data, which is a qualitative rather than a quantitative technique.     

(Perhalogenmethylthio)heterocyclen. X. Säurekatalysierte Substitutionen an (Perchlorfluormethylthio)pyrrolen und deren agrobiologische Wirkung

(Perhalomethylthio)heterocycles. X

1 IX. Mitt.: s. [1].

. Acid-catalyzed substitutions on (perchlorofluoromethylthio)pyrroles and their agro-biological activities In the presence of C₄F₉SO₃H the (perhalomethylthio)pyrroles 1a–c react with Cl_3?nF_nCSCl (n = 1–3) to give mixtures of the 2,5- and 2,4-disubstituted pyrroles 2a–f and 3a–h . 2a and 3a react with CF₃SCl (catalyst CF₃SO₃H) yielding 2,3,5-tris (trifloromethylthio)pyrrole ( 4a ), which under similar conditions reacts further to give 2,3,4,5-tetrakis (trifluoromethylthio)pyrrole ( 5 ). As a by-product during the conversion of 3a to 4a 2,3,4-tris (trifluoromethylthio)pyrrole ( 4b ) is formed. The pyrroles 2a , 4a and 5 form the mercury salts 6a–c ; compound 5 yields also a silver salt 7 . The ¹H- and ¹⁹F-NMR. spectra are discussed and the agro-biological properties of the compounds investigated.     

Übergangsmetall-thioketen-komplexe: VII. Erzeugung eines vinyliden-liganden aus einem thioketen durch schwefelabspaltung

The thioketene iron cluster (CH₃)₄C₆H₆CS(PPh₃)₂(CO)₄Fe₂S (I) reacts with thioketene in excess quantitatively to a vinylidene complex, as confirmed by X-ray analysis.     

β-Polycarbonylverbindunge, 5. Mitt.: 1,3-Diaminobenzole durch Acylierung von Di-enaminen

Zusammenfassung Die Reaktion von 1,3-Bis-dimethylamino-1,3-dienen mit Säurechloriden zu substituierten 1,3-Diaminbenzolen wird beschrieben.

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The reaction of 1,3-bis-dimethylamino-1,3-dienes with acyl chlorides to substituted 1,3-diaminobenzenes is described.

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Herrn Prof. Dr.L. Schmid zum 70. Geburtstag in Verehrung gewidmet.

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4. Mitt.:Ulrich Schmidt undM. Schwochau, Tetrahedron Letters 1967, 4491.     

Enzyme-purification and catalytic transformations in a microstructured PASSflow reactor using a new tyrosine-based Ni-NTA linker system attached to a polyvinylpyrrolidinone-based matrix

The synthesis of a Ni-nitrilotriacetic acid (Ni-NTA) attached via a new tyrosine-based linker matrix on monolithic crosslinked poly(vinyl benzyl chloride)/poly(vinylpyrrolidinone) is described. This matrix is incorporated inside a microstructured PASSflow reactor which was used for automatic purification and immobilisation of His(6)-tagged proteins. These could be used as stable and highly active biocatalysts for the synthesis of (R)-benzoin (6), (R)-2-hydroxy-1-phenylpropan-1-one (7) and 6-O-acetyl-D-glucal (17) in a flow-through mode.