1.3- Thiazolium-4-olate

Thiazolium-4-olat 3-MethyI-2-methylthio-5-phenyl- E8b, 192 (3-CH3 — 4-oxo — 5-Ar — 2-thio-no — 1,3-thiazolidin +... 

Tab.27 1,3-Thiazolium-4-olate aus monosubstituiertcn Amino-thiocarbonyl-Verbindungen und Carbonsaure-Derivaten mit a-standiger Ab-... 

R1 RJ R3 X Y Reaktionsbedingungen. ..-1,3-thiazolium-4-olat [%] Schmp. [°C] Lite- ratur... 

Substituierte 2-Thiono-2,3-dihydro-l,3-thiazole bzw. 4-Oxo-2-thiono-l,3-thiazolidine lassen sich durch Alkylierung am exo-cyclischen S-AtOm in 2-Alkylthio-l,3-thiazolium-Salze oder 2-Alkylthio-1,3-thiazolium-4-olate uberfiihren ... 

Nach dieser Methode konnen leicht auch 1,3-Thiazolium-4-olate hergestellt werden, wenn man von N-substituierten Thiocarbonsaure-amiden ausgeht. 

Die Synthese ist nicht fur 2-Phenoxy-substituierte Verbindungen geeignet. Vielmehr werden bei Einsatz von N-Phenyl-thiocarbamidsaure-phcnylester 2-Cyan-1,3-thiazolium-4-olate erhalten, da es zum Austausch der 2-Phenoxy-Gruppe durch abgespaltenes Cyanid kommt544 z. B, ... 

Wird 2,3,5-Triphenyl-1, 3-thiazolium-4-olat bei Bestrahlung mit Tributylphosphan entschwefelt, bildet sich unter Geriistumlagerung 2,3-Diphenyl-4-hydroxy-chinolin (78%)1638 ... 

The regiospedfic [3+2] 1,3-dipolar cycloaddition of 2-amino-1,3-thiazolium-4-olates (2-aminothioisomunchnones) to methyl propiolate to form pyridone derivatives has been investigated. In this study a dipolarophile, 13, was tethered to 1-amino-1-deoxy-D-glucitol pentaacetate and formed pyridone 14 upon 1,3-dipolar cycloaddition to but-2-yndioic acid dimethyl ester. ... 

Ein Quecksilber-Iod-Austausch ist auch an einem zwitterionischen Thiazolium-olat demon-striert worden815 z. B. ... 

Dipolar cycloaddition reactions of thioisoraunchnones (l,3-thiazolium-4-olates) have not been as extensively studied as those of munchnones (l,3-oxazolium-5-olates) despite offering rapid access to novel heterocyclic compounds. The cycloaddition of the thioisomunchnone (52) with trans-P-nitrostyrene results in the formation of two diastereoisomeric 4,5-dihydrothiophenes (53) and (54) via transient cycloadducts. These cycloadducts then undergo rearrangement under the reaction conditions <96JOC3738>. 

Reaction with acetylenic dipolarophiles represents an efficient method for the preparation of 2,5-dUiydrothiophenes. These products can be either isolated or directly converted to thiophene derivatives by dehydration procedures. The most frequently used dipolarophile is dimethyl acetylenedicarboxylate (DMAD), which easily combines with thiocarbonyl yhdes generated by the extrusion of nitrogen from 2,5-dihydro-1,3,4-thiadiazoles (8,25,28,36,41,92,94,152). Other methods involve the desUylation (31,53,129) protocol as well as the reaction with 1,3-dithiohum-4-olates and l,3-thiazolium-4-olates (153-158). Cycloaddition of (5)-methylides formed by the N2-extmsion or desilylation method leads to stable 2,5-dUiydrothiophenes of type 98 and 99. In contrast, bicyclic cycloadducts of type 100 usually decompose to give thiophene (101) or pyridine derivatives (102) (Scheme 5.37). 

In contrast to thiomiinchnones, thioisomiinchnones (5) (l,3-thiazolium-4-olates) have received considerable attention over the past three decades, and a rich array of 1,3-dipolar cycloaddition chemistry is described in Section 10.2.5. These heterocycles were initially constructed by Potts (1,53,57) from thioamides and a-halo acid chlorides, an example of which is shown in Scheme 10.17 (58). 

Somewhat earlier, Souizi and Roberts (63) reported mesoionic heterocycle interconversions leading to l,3-thiazolLum-4-thiolates, l,3-thiazolium-4-olates, and l,3-dithiolium-4-thiolates from l,3-dithiolium-4-olates. This elegant chemistry, which involves cycloaddition reactions, is presented in Section 10.3.8. 

Avalos and co-workers (220-228) extensively investigated the 1,3-dipolar cycloaddition chemistry of 2-aminothioisomiinchnones with both acetylenic and olefinic dipolarophiles. For example, sugar derivatives of the mesoionic imi-dazo[2,l-Z7]thiazolium-3-olate system react regioselectively with a variety of acetylenic dipolarophiles [DMAD, diethyl azodicarboxylate (DEAD), methyl propiolate, ethyl phenylpropiolate] to give the corresponding imidazo[l,2-a]pyr-idin-4-ones (e.g., 323) following sulfur extrusion from the not isolable cycloadducts (220). Similarly, these thioisomtinchnones react with diethyl azodicarboxylate and arylisocyanates in the expected fashion (221), and also with aryl aldehydes to form episulfides (222). 

Robert and co-workers (239,240) discovered novel conversions of 2-amino-1,3-dithiolium-4-olates (348) into other mesoionic heterocycles. For example, reaction of 348 with carbon disulfide, phenyl isocyanate, or phenyl isothiocyanate affords l,3-dithiolium-4-thiolates (349), l,3-thiazolium-4-olates (350), and 1,3-thiazolium-4-thiolates (351), respectively. Some of these reactions proceed via the ring-opened ketene tautomer of 348 (240). 

The reactions of l,3-thiazolium-4-olates with aliphatic aldehydes carried out in refluxing benzene or dichloromethane, have been reported to produce a series of highly functionalized (3-lactams and thiiranes at the same time [230]. The critical issue of the stereoselection was discussed in terms of the endo and exo approaches (respective to the aldehyde substituent) to any enantiotopic face of the heterocyclic dipole. Such orientations involved either the Re or the Si faces of the prochiral aldehydes (Scheme 105). 

Treatment of l,3-thiazolium-4-olates 526 with aliphatic aldehydes yielded a series of highly functionalized azetidin-2-ones 527 (Equation 216) <2003JOC6338>. The formation of this compound has been explained by ring fragmentation of an initial [3+2] cycloadduct. 

Examples of these systems are the l,2-dithiole-3-thione 43 and the type A mesoionic l,3-thiazolium-4-olate 44. Important members of this class are the tetrathiafulvalenes (TTFs) 45 and related systems, which have been studied extensively because of their potentially useful electrical properties . 

Ring closure of the precursor 257 under acid cyclodehydration conditions gives the mesoionic thiazolium-5-olate system 258 (Scheme 126) . 

Addition of l,3-thiazolium-4-olates to (l-alkynyl)carbene tungsten complexes lb,n affords thiophene and/or pyridone complexes, 64 and 65, by extrusion of sulfur and isocyanate, respectively, from the [3+2] adduct formed initially (Scheme 21).97 [3+2] cycloaddition reactions of azomethine... 

Reaction of 3-(4-methoxyphenyl)-2-(W-methyl)benzylamino-5-phenyl-l,3-thiazolium-4-olate 382 with benzalde-hyde or 4-nitrobenzaldehyde in dichloromethane at room temperature gave corresponding thiiranes in 63% and 15% yields (Scheme 111). Reaction of 383 with tetra-O-acetyl-D-arabinose in refluxing benzene for 1 h gave a mixture of thiiranes 384 in 45-50% yield (Scheme 112) <2001TA2265, 2003JOC6338>. 

The photochemical desulfurization of 4-amino-l,3 tWazolium salts 224 or mesoionic 2,3,5-triaryl-l,3-thiazolium-4-olates 228 in the presence of trialkylphosphite or trialkylphosphine, affording ring-opened cinnamic acid derivatives 226 [88JCS(P1)189] and 230 (83JHC245) or quinolinones 231 [88JCS(PI)189] is assumed to proceed via intermediate azetine derivatives 225 and 229, respectively (Scheme 62). 

Reaction of 2,3-diphenylcyclopropenethione and the mesoionic thiazole, 2-aryl-3-phenyl-thiazolium-4-olate, in benzene yielded the 1 1 cycloadducts, 8-thia-6-azabicyclo[3.2.1]oct-2-ene-4-thiones 8. ... 

Mesoionic thiazoles represent masked ylides which can undergo cycloaddition reactions. 1,3-Thiazolium-5-olate (73) and thioisomunchnone (74) can be considered as an azomethine ylide dipole and a thiocarbonyl ylide dipole, respectively. The cycloaddition chemistry of these compounds have been studied and their utility for the synthesis of heterocycles demonstrated <94S993>. 

Imidazo[2,l-h]thiazolium-3-olate 160 (Section VI,C Scheme 47) underwent rapid cycloaddition with acetylene mono- and dicarboxylic esters to give the imidazo[l,2-a]pyridin-3-yl acyclo C-nucleoside 208 through sulfur extrusion from the intermediate 207 (91MI7) (Scheme 62). 

In einem zweistufigen ProzeB ist 5-Acetyl-2,3-diphenyl-l, 3-thiazolium-4-olat (Schmp. 245-247°) aus Mercapto-essigsaure und Benzoesaure-chlorid-phenylimid zuganglich579. 

C H5 c6h5 H Br OH Benzol/(H5C2)3N 20 4 2,3-Diphenyl-l, 3-thiazolium-4-olat 38 113-115 (Zers.) 573... 

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