Sample records for azirines

  1. Cycloaddition of methyl 2-(2,6-dichorophenyl)-2H-azirine-3-carboxylate to electron rich 2-azadienes


    Alves, M. José; Durães, M. Miguel; Fortes, A. Gil


    Tert-Butyldimethylsililoxy-2-aza-1,3-butadienes react with 2H-azirine 3 leading to Diels-Alder cycloadducts in moderate yields. The reactions are endo- and regio- selective with the azirine being added by its less hindered face. There is only one product in the case of 1b, 4b. There are two isomers (4 and 5) from 1a, 1c and 1d. A different result was obtained with the diene 1e. Diene 1e formed products 4e and 8. Some of compounds 4 and 5 have been hydrolysed leading to functionalized aziridin...

  2. Diels-alder cycloaddition of 2-azadienes to methyl 2-(2,6-dichlorophenyl)-2H-azirine-3-carboxylate in the synthesis of methyl 4-oxo-1,3-diazabicyclo[4.1.0]heptane-6-carboxylates


    Alves, M. José; Durães, M. Miguel; Fortes, A. Gil


    A number of fused 4-oxo-1,3-diazabicyclo[4.1.0]heptane-6-carboxylates, a new type of compound, have been obtained by Diels-Alder cycloaddition between nucleophilic 2-azadienes and an electrophilic 2H-azirine. The reactions are completely endo- and regioselective, the azirine being added by its less hindered face to the diene. There are two isomers 7 and 8 formed from dienes 1 due either to isomerization of the cycloadducts 7 and 8 or by isomerization of the C=N bond of the diene during the re...

  3. Azirinium ylides from α-diazoketones and 2H-azirines on the route to 2H-1,4-oxazines: three-membered ring opening vs 1,5-cyclization

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    Nikolai V. Rostovskii


    Full Text Available Strained azirinium ylides derived from 2H-azirines and α-diazoketones under Rh(II-catalysis can undergo either irreversible ring opening across the N–C2 bond to 2-azabuta-1,3-dienes that further cyclize to 2H-1,4-oxazines or reversibly undergo a 1,5-cyclization to dihydroazireno[2,1-b]oxazoles. Dihydroazireno[2,1-b]oxazoles derived from 3-aryl-2H-azirines and 3-diazoacetylacetone or ethyl diazoacetoacetate are able to cycloadd to acetyl(methylketene generated from 3-diazoacetylacetone under Rh(II catalysis to give 4,6-dioxa-1-azabicyclo[3.2.1]oct-2-ene and/or 5,7-dioxa-1-azabicyclo[4.3.1]deca-3,8-diene-2-one derivatives. According to DFT calculations (B3LYP/6-31+G(d,p, the cycloaddition can involve two modes of nucleophilic attack of the dihydroazireno[2,1-b]oxazole intermediate on acetyl(methylketene followed by aziridine ring opening into atropoisomeric oxazolium betaines and cyclization. Azirinium ylides generated from 2,3-di- and 2,2,3-triaryl-substituted azirines give rise to only 2-azabuta-1,3-dienes and/or 2H-1,4-oxazines.

  4. Investigation on the reactivity of α-azidochalcones with carboxylic acids: Formation of α-amido-1,3-diketones and highly substituted 2-(trifluoromethyloxazoles

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    Kandasamy Rajaguru


    Full Text Available The reaction of α-azidochalcones with carboxylic acids has been investigated resulting in the formation of α-amido-1,3-diketones under microwave irradiation via in situ formation of 2H-azirine intermediates. An interesting reaction is described wherein, with trifluoroacetic acid at lower temperature, it affords highly substituted 2-(trifluoromethyloxazoles. These flexible transformations proceed under solvent free conditions in good to excellent yields without any catalyst.

  5. Visible-Light-Induced Click Chemistry. (United States)

    Mueller, Jan O; Schmidt, Friedrich G; Blinco, James P; Barner-Kowollik, Christopher


    A rapid and catalyst-free cycloaddition system for visible-light-induced click chemistry is reported. A readily accessible photoreactive 2H-azirine moiety was designed to absorb light at wavelengths above 400 nm. Irradiation with low-energy light sources thus enables efficient small-molecule synthesis with a diverse range of multiple-bond-containing compounds. Moreover, in order to demonstrate the efficiency of the current approach, quantitative ligation of the photoactivatable chromophore with functional polymeric substrates was performed and full conversion with irradiation times of only 1 min at ambient conditions was achieved. The current report thus presents a highly efficient method for applications involving selective cycloaddition to electron-deficient multiple-bond-containing materials.

  6. The synthesis of (R)- and (S)-[N-methyl-{sup 11}C]{beta}, {beta}-difluoromethamphetamine for the investigation of the binding mechanism of biogenic amines in vivo

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    Gillings, N.M.; Gee, A.D. [PET Centre, Aarhus University Hospital, Aarhus C (Denmark); Inoue, O. [School of Allied Health Sciences, Osaka University Medical School, Osaka (Japan)


    In an attempt to elucidate the contribution of the extent of nitrogen protonation on the in vivo binding of methamphetamine in the brain, the enantiomers of [N-methyl-{sup 11}C]{beta},{beta}-difluoroamphetamine (4) were prepared for use in positron emission tomography (PET) studies. Thus, the enantiomers of {beta},{beta}-difluoroamphetamine were prepared from trans-{beta}-methylstyrene, via bromination, conversion into the azirine, fluorination and resolution as the tartrate salts. (R)- and (S)-{beta},{beta}-difluoroamphetamine (3) were then each labelled with carbon-11 (t{sub 1/2}=20.4 min) by N-methylation of the corresponding homochiral {beta},{beta}-difluoroamphetamine with [{sup 11}C]methyl iodide. The labelled products were each synthesised, purified and formulated in 35 min, starting from [{sup 11}C]carbon dioxide in 15-16% decay-corrected radiochemical yield, with a radiochemical purity of >99% and specific radioactivity of 50-150 GBq {mu}mol{sup -1} at end of synthesis.