Facile synthesis of reactive benzoazetinone by flash vacuum pyrolysis of isatoic anhydride

Chiu, Shao-Jung; Chou, Chin-Hsing

doi:10.1016/s0040-4039(99)01838-9

Cited by 15 publications

(8 citation statements)

References 10 publications

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“…Pyrazolotriazinone 4 could undergo nitrogen extrusion by a retro‐Diels–Alder reaction, as was proposed for the thermolysis of pyrrolotriazines 9 , or following ring‐opening, as was proposed for the photochemical reactions of benzotriazinones . Elimination of nitrogen from 4 could lead to the imidoylketene 6 or even an azetinone intermediate, which can coexist in equilibrium , . These intermediates could react with a nucleophile, in this case a second molecule of 4 or a better suited tautomer of it, to give the final product 5 .…”

Section: Resultsmentioning

confidence: 92%

“…[17] Elimination of nitrogen from 4 could lead to the imidoylketene 6 or even an azetinone intermediate, which can coexist in equilibrium. [15,[18][19][20][21][22] These intermediates could react with a nucleophile, in this case a second molecule of 4 or a better suited tautomer of it, to give the final product 5. Similar nucleophilic reactions have previously been reported for benzoazetinones to give aminobenzamides and anthranilate esters.…”

Section: Resultsmentioning

confidence: 99%

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Thermal Ring‐Opening of Pyrazolo[3,4‐d][1,2,3]triazin‐4‐ones: An Experimental and Theoretical Study

et al. 2018

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Several 3‐pyrazolylcarbonyl‐pyrazolo[3,4‐d][1,2,3]triazin‐4‐ones have been prepared from 5‐amino‐1H‐pyrazole‐4‐carbonitriles through a simple sequence. In the first step, diazotization of the corresponding aminopyrazoles afforded pyrazolo[3,4‐d][1,2,3]triazin‐4‐ones. Next, thermal rearrangement of these compounds through nitrogen elimination gave the final products. The proposed mechanism for the ring‐opening of the pyrazolotriazinones to give the pyrazolylcarbonyl‐pyrazolotriazinones involves the generation of an iminoketene intermediate, which reacts with a second molecule of pyrazolotriazinone. The complete mechanism of product formation involving the iminoketene intermediate, and all other reasonable pathways, have been explored in detail through DFT calculations. Furthermore, additional experiments to corroborate the presence of the iminoketene intermediate were carried out.

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Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Thermal Ring‐Opening of Pyrazolo[3,4‐d][1,2,3]triazin‐4‐ones: An Experimental and Theoretical Study

et al. 2018

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“…15b). 42 To our knowledge, only few examples of N-tert-alkylbenzoazetinones obtained by ring opening/recyclization of anthranilium ions, proved to be sufficiently stable to be isolated and characterized. 43…”

Section: X-ray Crystallographymentioning

confidence: 99%

Synthesis, structural properties, and pharmacological evaluation of 2-(acylamino)thiophene-3-carboxamides and analogues thereof

et al. 2014

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We have previously reported the synthesis and the pharmacological characterization of a family of methyl 2-(acylamino)thiophene-3-carboxylates as GABA B positive allosteric modulators active both in vitro and in vivo. In the present work, we describe the synthesis of new compounds based on the bioisosteric replacement of the ester moiety with amido or heterocyclic groups as well as of thieno[2,3-d]pyrimidine derivatives as rigid analogues thereof. 4H-Thieno[2,3-d][1,3]oxazin-4-ones were used as synthetic intermediates for the preparation of some of these compounds. The structures of oxazinones 11b, 16, and 17 were assigned by X-ray crystallographic studies, which definitely ruled out the isomeric betalactam structure previously hypothesized for these compounds. None of the new molecules exhibited significant activity at the GABA B receptor, either as allosteric or orthosteric ligands.

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“…Pyrolysis of isatoic anhydride, followed by trapping of the products at 77 K, was reported to yield benzoazetinone itself. 6 Similarly, trapping of the products of 1-methyl-1,2,3-benzotriazin-4(1 H )-one pyrolysis in a layer of solid argon at 15 K led to stabilization of N -methylbenzoazetinone in an Ar matrix. 7 UV-induced decarbonylation of N -methoxyisatin isolated in an Ar matrix yielded N -methoxybenzoazetinone.…”

Section: Introductionmentioning

confidence: 99%

“…In contrast to that, the energy of the closed-ring structure of benzoazetinone is lower (by more than 30 kJ mol –1 ) than that of its open-ring α-iminoketene isomer. Although benzoazetinones are highly reactive and difficult to obtain, there are several reports on successful preparation of benzoazetinone or its derivatives. − Only some N -alkylbenzoazetinones with tertiary alkyl groups can be stable at room temperature. Pyrolysis of isatoic anhydride, followed by trapping of the products at 77 K, was reported to yield benzoazetinone itself .…”

Section: Introductionmentioning

confidence: 99%

Photochemical Generation of Benzoazetinone by UV Excitation of Matrix-Isolated Precursors: Isatin or Isatoic Anhydride

2020

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Benzoazetinone was photochemically generated by UV irradiation of isatin isolated in low-temperature Ar matrixes. Upon UV (λ = 278 nm) excitation of isatin, monomers of the compound underwent decarbonylation and the remaining part of the molecule adopted the benzoazetinone structure or the structure of its open-ring isomer α-iminoketene. The same products (benzoazetinone and α-iminoketene) were generated by UV (λ = 278 nm) induced decarboxylation of matrix-isolated monomers of isatoic anhydride. Photoproduced α-iminoketene appeared in the low-temperature matrixes as a mixture of syn and anti isomers. Photoproducts generated upon λ = 278 nm irradiation of matrix-isolated isatin were subsequently exposed to λ = 532 nm light. That irradiation resulted in the shift of the α-iminoketene–benzoazetinone population ratio in favor of the latter closed-ring structure. The next irradiation at 305 nm caused the shift of the α-iminoketene–benzoazetinone population ratio in the opposite direction, that is, in favor of the open-ring isomer. Neither benzoazetinone nor its α-iminoketene open-ring isomer was generated upon UV (λ = 278 nm) irradiation of phthalimide isolated in Ar matrixes. Instead, the UV-excited monomers of this compound underwent such phototransformations as oxo → hydroxy phototautomerism or degradation of the five-membered ring with release of HNCO and CO. The efficiency of these photoconversions was low.

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Facile synthesis of reactive benzoazetinone by flash vacuum pyrolysis of isatoic anhydride

Cited by 15 publications

References 10 publications

Thermal Ring‐Opening of Pyrazolo[3,4‐d][1,2,3]triazin‐4‐ones: An Experimental and Theoretical Study

Thermal Ring‐Opening of Pyrazolo[3,4‐d][1,2,3]triazin‐4‐ones: An Experimental and Theoretical Study

Synthesis, structural properties, and pharmacological evaluation of 2-(acylamino)thiophene-3-carboxamides and analogues thereof

Photochemical Generation of Benzoazetinone by UV Excitation of Matrix-Isolated Precursors: Isatin or Isatoic Anhydride

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