Spontaneous chiral resolution of a coordination polymer with distorted helical structure consisting of achiral building blocks.

The biohydrolysis of differently para-substituted styrene oxide derivatives was studied, using whole cells of the fungi Aspergillus niger or Beauveria sulfurescens. These microorganisms proved to be equipped with epoxide hydrolases which are able to achieve these hydrolyses with high enantioselectivity. This allowed the preparation of the optically active epoxides and of the corresponding vicinal diols which were obtained with good to excellent enantiomeric purity. These two microorganisms proved to be enantiocomplementary. A mechanistic study, carried out using a crude lyophilized enzymatic extract from A. niger, indicated via Hammet coefficient plotting that this hydrolysis is very probably due to a general base-catalyzed process.

Microbiological Transformations. 33. Fungal Epoxide Hydrolases Applied to the Synthesis of Enantiopure Para-Substituted Styrene Oxides. A Mechanistic Approach.

2.08 – Pyridines and their Benzo Derivatives: (v) Synthesis

Publisher Summary This chapter presents the literature for pyrans, thiopyrans, and selenopyrans. Pyran structure refers to a six-membered ring possessing one oxygen, sulfur, selenium, or telurium heteroatom singly bonded in a cyclic system of two double bonds and one tetrahedral atomic center. The pyrans, thiopyrans, and selenopyrans can be synthesized using acyclic or cyclic precursors that indicate if a pyran ring closure does or does not occur during synthesis. Reactions such as (1) oxidation, (2) disproportionation, (3) hydrogenation and reduction, (4) desulfurization of thiopyrans, (5) isomerization, (6) ring-opening reactions, (7) substitution reactions, and (8) conversion to carbocyclic systems (outline the chemical properties of pyrans, thiopyrans, and selenopyrans. Pyrans are very rare as natural products. Only some 2H-pyrans have been isolated from plants. The chapter finally describes the physical properties of triazolopyridines such as electronic spectra, infrared spectra, nuclear magnetic resonance, mass spectra, and some other miscellaneous properties.

Pyrans, thiopyrans, and selenopyrans

There are provided novel compounds of formula (I), wherein R1, R2, R4, R5, G1, G2, L, Y and n are as defined in the Specification and optical isomers, racemates and tautomers thereof, and pharmaceutically acceptable salts thereof; together with processes for their preparation, compositions containing them and their use in therapy. The compounds are inhibitors of neutrophil elastase.

2-pyridone derivatives as neutrophil elastase inhibitors and their use

Reaktionen von Diazoalkanen mit α‐Diketonen und Chinonen, XXIV1)Synthese und Reaktionen substituierter Pyrrolin‐2,3‐dione mit Diazoalkanen

2,3-Dichlor-p-benzochinon (1) addiert Diazomethan und Diazoathan primar an die unsubstitutierte Doppelbindung unter Bildung der nicht isolierten 1-Pyrazoline 2 Diese werden, nach Isomerisierung zu 2-pyrazolinen 3, durch uberschussiges Chinon 1 zu den Pyrazolen 4 und 5 dehydriert, die nun mit Diazoalkanen unter N-Alkylierung zu den isomeren Indazolen 8 und 9 weiterreagieren Bei Uberschus an Diazomethan entsteht das Epoxid 13, wahrend mit grosem Uberschus an Diazomethan entsteht das Epoxid 13, wahrend mit grosem Uberschus and Diazoathan das Ringerweiterungsprodukt 14 und das Dipyrazolochinon 15 gebildet werden



Reaction of Quinones and αDicarbonyl Compounds with Diazoalkanes, XXII Reaction of 2,3-Dichloro-pbenzolquinone with Diazoalkanes



2,3-Dichloro-p-benzoquinone (1) adds diazomethane and diazoethane to the unsubstituted double bond to form 1-pyrazolines 2 (not isolated) as the primary products After isomerising to 2-pyrazolines 3 these are dehydrogenated to the pyrazoles 4 and 5, which further react with diazoalkanes to yield the two isomeric indazoles 8 and 9 With an excess of diazomethane the epoxide 13 is produced while with a great excess of diazoethane the ring-enlarged product 14 and the dipyrazolo-quinone 15 are formed

Reaktionen von Diazoalkanen mit α‐Diketonen und Chinonen, XXII. Umsetzungen von 2,3‐Dichlor‐p‐benzochinon mit Diazoalkanen

Das 2,6-Diphenyl(thio)pyrylium-perchlorat 1a,b reagiert mit den 6-Ring-β-Diketonen in Gegenwart von basischen Katalysatoren zu den (Thio) Pyranyliden- Verbindungen 2a-k, wahrend mit den hoheren 1,3-Cycloalkandionen (n = 7–12) die primar gebildeten Kupplungsprodukte 6a–1 isoliert werden. die durch Oxidation die Pyranylidenderivate 7a–1 liefern. Bei der Kondensation der β-Diketone mit 4-Chlorthiopyrylium-salzen 8b entstehen 2h–j und 7g-1. 8a liefert bei der Umsetzung mit 9a–c die Tetrahydro-2H-benzopyranderivate 10a-c Die Reaktion primarer Amine (Methyl-und Athylamin) mit 2a–c fuhrt zu den Hydrochinolinderivaten 13a–c. Dagegen lassen sich 2e–g mit primaren Aminen in Pyridinderivate 14a–c uberfuhren. Beim Erhitzen von 2a–c mit alkohol. KOH und Kurzem Erwarmen mit Salzsaure erhalt man die Tetrahydro-4H-benzopyranderivate 15a–c. Die spektroskopischen Eigenschaften der Verbindungen werden diskutiert.



Reactions of 2,6-Diphenyl(thio)pyrylium Salts with 1,3-Cycloalkanediones



2,6-Diphenyl(thio)pyrylium perchlorate 1a,b reacts with 6-ring-β-diketones in the presence of basic catalysts to yield (thio)pyranyliden compounds 2a-k. With higher membered 1,3-cycloalkanediones (n = 7 – 12) it gives the primary reaction products 6a–1, which on oxidation afford the pyranyliden derivatives 7a–1. The condensation of β-diketones with 4-chlorothiopyrylium salts 8b yields 2h-j and 7g–1 The reaction of 8a with 9a–c leads to tetrahydro-2H benzopyran derivatives 10a–c Treatment of 2a–c with primary amines (methyl-and ethylamine) gives the hydroquinoline compounds 13a–c, whereas 2e–g form the pyridine derivatives 14a–c By heating 2a–c with alcohol. KOH, Acidification with hydrochloric acid and Subsequent refluxing for a short time one gets the tetrahydro-4H-benzopyran compounds 15a–c. The spectroscopic properties of these Compounds are discussed.

Umsetzungen von 2,6‐Diphenyl(thio)pyrylium‐Salzen mit 1,3‐Cycloalkandionen

Reaktionen von Diazoalkanen mit α‐Diketonen und Chinonen, XXV1) Umsetzungen von Polymethylen‐1‐phenylpyrrolin‐2,3‐dionen mit Diazoalkanen

4-Chlor-2,6-bis(methylthio)thiopyrylium-perchlorat (3) kondensiert mit CH-aciden Verbindungen in Gegenwart von Triathylamin unter Bildung der entsprechenden Thiopyranyliden-Derivate 2a–s. Die Beteiligung dipolarer Grenzstrukturen am Grundzustand von 2 wird anhand spektroskopischer Eigenschaften diskutiert.



A Novel Method for the Synthesis of Thiopyranylidene Compounds



4-Chloro-2,6-bis(methylthio)thiopyrylium perchlorate (3) condenses with CH-acidic compounds in the presence of triethylamine to form the corresponding thiopyranylidene derivatives 2a–s. The contribution of dipolar mesomeric structures to the ground state of 2 is discussed by means of spectroscopical data.

Thommen J. Arackal

Papers

Reaktionen von Diazoalkanen mit α‐Diketonen und Chinonen, XXIV1)Synthese und Reaktionen substituierter Pyrrolin‐2,3‐dione mit Diazoalkanen

Reaktionen von Diazoalkanen mit α‐Diketonen und Chinonen, XXII. Umsetzungen von 2,3‐Dichlor‐p‐benzochinon mit Diazoalkanen

Umsetzungen von 2,6‐Diphenyl(thio)pyrylium‐Salzen mit 1,3‐Cycloalkandionen

Reaktionen von Diazoalkanen mit α‐Diketonen und Chinonen, XXV1) Umsetzungen von Polymethylen‐1‐phenylpyrrolin‐2,3‐dionen mit Diazoalkanen

Neue Methode zur Darstellung von Thiopyranyliden‐Verbindungen