1,2-Diazetines as Useful Tools for Ring Transformation Reactions with Isothiocyanates – A New Entry to 1,3,4-Thiadiazines

Beckert, Rainer; Fleischhauer, J.; Darsen, Anja; Weston, Jennie; Schenk, Stephan; Batista, Ariadna; Anders, Ernst; Pufky, Daniela; Walter, Olaf; Görls, Helmar; Döring, Manfred

doi:10.3987/com-05-10349

Cited by 10 publications

(10 citation statements)

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“…These esters were converted directly into their imino homologues without changing the solvent. After removing the solvent, addition of NH 4 Cl, and heating in mesitylene, the desired fluorubines 3 were furnished in comparable yields. We would like to note that this way is a bit more practicable, because it is not recommended to change the solvents before the final cyclization step.…”

Section: Full Papermentioning

confidence: 99%

“…In a final step, the solvent was changed once again into DMF, NH 4 Cl was added, and the mixture was heated in a sealed tube at 160 8C for 24 h. Under these conditions, most likely the intramolecular formation of a cyclic aminal 10-B takes place, which finally, upon protonation and elimination of ammonia, formed the cationic fluorubine derivatives 3. In a second protocol, we activated the cyclic amide substructure with trifluoromethanesulfonic anhydride (Tf 2 O) in dichloromethane, [16] which also leads to bisA C H T U N G T R E N N U N G (iminium) salts 10-D originating from oxygen sulfonation by formation of esters of trifluoromethanesulfonic acid (Scheme 4).…”

Section: Full Papermentioning

confidence: 99%

“…[3] Due to their ring strain, these four-ring systems proved to be valuable starting materials for transformation reactions to yield several, in a wide range of variable substitutable, five-and six-membered heterocycles. [4] Surprisingly, cationic derivatives of fluorubines (dihydro-5,6,7,12,13,14-hexaazapentacenes) 3 were identified as byproducts in some cases. These Abstract: The reaction of bisA C H T U N G T R E N N U N G (imidoyl) chlorides of oxalic acid with monoalkyl hydrazines leads to substituted D 2 -1,2-diazetines, which are versatile building blocks for ring-transformation reactions.…”

Section: Introductionmentioning

confidence: 99%

“…By using toluene as a solvent in this reaction step, the formation of a yellow precipitate was detected, thus supporting our assumption. After removing and changing the solvent into THF, dried ammonia was passed through the reaction flask and the formation of a sluggish mixture was observed containing NH 4 Cl and the possible bisA C H T U N G T R E N N U N G (imino)-derivatives 10-B. Due to the scrupulous sensitivity of these intermediates against moisture, whereby …”

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From Byproducts to Efficient Fluorophores: A Route to the Synthesis of Fluorubines

Fleischhauer¹,

Beckert²,

Jüttke³

et al. 2009

Chemistry A European J

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The reaction of bis(imidoyl) chlorides of oxalic acid with monoalkyl hydrazines leads to substituted Delta(2)-1,2-diazetines, which are versatile building blocks for ring-transformation reactions. One remarkable product originating from side reactions featured by a strong orange/red fluorescence was confirmed as a novel fluorubine derivative. In continuing our studies to substituted oligoazaacenes, we developed several synthetic entries to build up novel fluorubine derivatives, in which particularly aminobridged bis(quinoxaline)s are the key products for cationic hexaazapentacenes. We would like to discuss the possible formation pathways of these fluorubine derivatives, which exhibit interesting photophysical and chemical properties. The structures of all new derivatives were confirmed by common analytical methods (NMR spectroscopy, CV, UV/Vis, mass spectrometry, elemental analysis, and X-ray structural analysis) and will be discussed on selected examples in more detail.

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Section: Full Papermentioning

confidence: 99%

Section: Full Papermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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From Byproducts to Efficient Fluorophores: A Route to the Synthesis of Fluorubines

Fleischhauer¹,

Beckert²,

Jüttke³

et al. 2009

Chemistry A European J

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“…Very recently, we could demonstrate that 1,2-diazetines undergo a ring transformation upon reaction with isothiocyanates to yield 1,3,4-thiadiazines. 3 Rearrangements involving group transfer reactions in amidines has been a growing area of research in the past two decades. 4 Acyl groups in amidine derivatives often undergo 1,3-displacement reactions under much milder conditions than those needed to effect the transfer of alkyl or aryl groups.…”

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Δ²-1,2-Diazetines: Regioselective Acylation Reactions and Rearrangement into 4H-1,3,4-Oxadiazines

Fleischhauer¹,

Beckert²,

Weston³

et al. 2006

Synthesis

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R e a r r a n g e m e n t R e a c t i o n s o f D 2 -1 , 2 -D i a z e t i n e s Abstract: Reaction of a 1-substituted D 2 -1,2-diazetine with acid chlorides or anhydrides resulted in the derivatives 3a,b,f that have been acylated at a ring position. On the other hand, trifluoroacetic anhydride yields a new 1,3,4-oxadiazine 4e under the same conditions. The structure of 4e could be confirmed by X-ray structural analysis. Acylated 1,2-diazetidines of type 3a,b can be nearly quantitatively transformed into 1,3,4-oxadiazines 4a,b by thermally induced ring-expansion reactions. Differential scanning calorimetry measurements provide evidence for a monomolecular mechanism in which a strong dependence of the acyl group on the rate of reaction is observed.Four-ring heterocycles that bear two nitrogen atoms in the ring positions 1 and 2 are quite rare, with only a few examples having been reported in the literature. 1 We have recently developed a procedure for synthesizing D 2 -1,2-diazetines which possess structural elements of cyclic amidines and amidrazones. 2 These compounds can also be classified as diazadienes, which may possibly be of value as ligands in metallocomplex chemistry. The nitrogen heteroatoms in these ring systems allow facile acylations. In addition, the inherent ring strain guarantees that such four-ring heterocycles are potential and possibly quite versatile building blocks for ring transformation reactions. Very recently, we could demonstrate that 1,2-diazetines undergo a ring transformation upon reaction with isothiocyanates to yield 1,3,4-thiadiazines. 3 Rearrangements involving group transfer reactions in amidines has been a growing area of research in the past two decades. 4 Acyl groups in amidine derivatives often undergo 1,3-displacement reactions under much milder conditions than those needed to effect the transfer of alkyl or aryl groups. Ring-expansion reactions upon acylation of four-membered heterocycles such as our recently developed 1,2-diazetines will hopefully extend the number of available cycloamidines available to researchers working in this field.Treatment of 1,2-diazetines 1 with acyl chlorides or anhydrides 2 in the presence of catalytic amounts of DMAP yields acylated 1,2-diazetidines of type 3 (Scheme 1). This acylation is quite fast and can easily be monitored by TLC.Although an exocyclic NH proton has been detected in solid-state structures of the starting material, 2 the ring nitrogen has been regioselectively acylated. DFT calculations [B3YLP/-6-31+G(d,p)] support these experimental findings in that the ring acylated product is ca. 9 kcal/mol more stable than the exocyclic product. 5The stability of the acylated diazetidine depends strongly upon the nature of the substituent R in the acylation reagent 2a-f employed. If R is a relatively soft electron-accepting substituent such as acetyl (2a) or pivaloyl (2b), the acylated diazetidines 3a,b can be isolated in quite good yields. These compounds show an absorption band at 375 nm in their UV/Vis spectra, which is characteristic...

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Ethyl Isothiocyanatoacetate

Wagger¹,

Kralj²,

Svete³

et al. 2008

Encyclopedia of Reagents for Organic Synthesis

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1,2-Diazetines as Useful Tools for Ring Transformation Reactions with Isothiocyanates – A New Entry to 1,3,4-Thiadiazines

Cited by 10 publications

References 4 publications

From Byproducts to Efficient Fluorophores: A Route to the Synthesis of Fluorubines

From Byproducts to Efficient Fluorophores: A Route to the Synthesis of Fluorubines

Δ²-1,2-Diazetines: Regioselective Acylation Reactions and Rearrangement into 4H-1,3,4-Oxadiazines

Ethyl Isothiocyanatoacetate

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1,2-Diazetines as Useful Tools for Ring Transformation Reactions with Isothiocyanates – A New Entry to 1,3,4-Thiadiazines

Cited by 10 publications

References 4 publications

From Byproducts to Efficient Fluorophores: A Route to the Synthesis of Fluorubines

From Byproducts to Efficient Fluorophores: A Route to the Synthesis of Fluorubines

Δ2-1,2-Diazetines: Regioselective Acylation Reactions and Rearrangement into 4H-1,3,4-Oxadiazines

Ethyl Isothiocyanatoacetate

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Product

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Δ²-1,2-Diazetines: Regioselective Acylation Reactions and Rearrangement into 4H-1,3,4-Oxadiazines