Synthese und physikalische Eigenschaften erster 3,3′‐verbrückter Bis‐ und Tris(1,3‐thiazolium‐4‐olate) sowie eines 5,5′‐verbrückten Bis(1,3‐thiazolium‐4‐olats) und seine überführung in 3,3′‐(1,4‐Phenylen)bis[2(1H)‐pyridinone]

Abstract

Die Synthcsc und physikalische Eigcnschaften der ncuen Titclverbindungen vom Typ 7, 9 und 12, die zwei oder in einem Fall drei mesoionische 1,3-Thiazol-4-on-Systeme enthalten, werden beschrieben. Mit Acetylendicarbonsiure-dimethylester oder Dibenzoylethin reagiert 12 unter Schwefel-Freisetzung zu den 3,3'-( 1,4-Phenylen)bis[2(1 H)-pyridinonl-Derivatcn 23a bzw. b.In Fortfuhrung unserer Studien iiber die Darstellung und Eigenschaften 2,2'-und 5,5'-verbriickter Bis(I,3-dithiolylium-4-0late)'~~) synthetisierten wir auch neue Bis(l,3-thiazolium-4-olate) sowie ein dreikerniges mesoionisches 1,3-Thiazol-4-on. Die Verbruckung der mesoionischen Heteroarene erfolgt dabei in drei Fallen iiber die 3-Stellungen und in einem Fall iiber die 5-Positionen.Hier berichten wir iiber die Synthese und physikalischen Eigenschaften solcher mesoionischer Systeme vom Typ 7, 9 und 12 sowie uber einige Cycloadditionen an Alkine. Synthese der 3,3'-verbriickten Bis-und Tris-(1,3-thiazolium-4-olate) 7 und 9Einen interessanten Zugang zu 3,3'-verbriickten mehrkernigen mesoionischen 1,3-Thiazol-4-onen eroffnet der bisher nur einmal bei der Darstellung eines einkernigen Vertreters realisierte Weg iiber die Umsetzung von 1,3-Dithiolylium-4-olaten mit primaren Aminen ' ). The synthesis and physical properties of thc novel title compounds of type 7, 9, and 12, which contain two or in one case three mesoionic 1,3-thiazol-4-one systems, are described. With dimethyl acetylenedicarboxylate or dibenzoylethyne, 12 reacts under elimination of sulfur to produce 3,3'-(1.4-phenylene)bis[f(l H)-pyridinone] derivatives 23a and b, respectively. Das fur die

Novel Difunctional Reversible Addition Fragmentation Chain Transfer (RAFT) Agent for the Synthesis of Telechelic and ABA Triblock Methacrylate and Acrylate Copolymers

“…Two analogues of CTA 1 (CTA 2 and CTA 3 , see Figure ) were synthesized for this study and the synthetic pathways are detailed in Scheme . The synthesis of CTA 2 has been previously reported by Gotthardt et al, although not to be used as a RAFT chain transfer agent; however, our modified method offers an improvement on the yield, and all starting materials are readily commercially available.

1 Synthesis of CTA 1 and CTA 3 (THF, Tetrahydrofuran; TEA, Triethylamine)

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Switchable Cycloadditions of Mesoionic Dipoles: Refreshing up a Regioselective Approach to Two Distinctive Heterocycles

“… 13 Also, pioneering work on the reactions of bridged bis- and tris(thiazolium-4-olates) evidenced the formation of pyridone derivatives after sulfur elimination. 14 When collectively considered, such facts still point to a prevalent steric control, although the substitution pattern at the parent mesoionic ring modulates the fragmentation to some extent. Alternative studies from our group, involving both mono- and bicyclic thioisomünchnones with double and triple bonds unveil actually stereoelectronic effects, with cycloadduct fragmentation being determined by donor–acceptor interactions at the saddle-point structures.…”

“…Unlike monocyclic thioisomünchnones, bicyclic and ring-fused thioisomünchnones usually favor the formation of six-membered rings, presumably by alleviating the steric hindrance in cycloadducts by sulfur extrusion, , whereas intramolecular reactions with propargylic groups afford thiophene and thiazole derivatives . Also, pioneering work on the reactions of bridged bis- and tris­(thiazolium-4-olates) evidenced the formation of pyridone derivatives after sulfur elimination . When collectively considered, such facts still point to a prevalent steric control, although the substitution pattern at the parent mesoionic ring modulates the fragmentation to some extent.…”