112135-47-4Relevant articles and documents
Chemistry of N,N-bis(silyloxy)enamines: Part 5 - Interaction with N-trialkylsilylated azoles. Convenient method for the synthesis of α-azolyl-substituted oximes
Lesiv, Alexey V.,Ioffe, Sema L.,Strelenko, Yury A.,Tartakovsky, Vladimir A.
, p. 3489 - 3507 (2002)
Aliphatic nitro compounds can be considered as good precursors of a wide variety of α-azolyl-substituted oximes. The double silylation of convenient aliphatic nitro compounds and the subsequent N,C-coupling of the resulting N,N-bis(silyloxy)enamines 3 with N-silylated azoles 4 lead to the formation of the silylated α-azolylsubstituted oximes 6, which can be smoothly desilylated to give the target α-azolyl-substituted oximes 5. The mechanism of the key step of this process - N,C-coupling - includes the generation of corresponding conjugated nitrosoalkenes 7 (Schemes 4 and 5). The contribution of the chain mechanism in the overall process is considered as well, The studies of the scope and limitations of this reaction, as well as the optimization of its conditions were accomplished. The configuration of the C=N bond in oximes was established by NMR.
Addition of HO-Acids to N,N-Bis(oxy)enamines: Mechanism, Scope and Application to the Synthesis of Pharmaceuticals
Naumovich, Yana A.,Golovanov, Ivan S.,Sukhorukov, Alexey Yu.,Ioffe, Sema L.
, p. 6209 - 6227 (2017/11/15)
The regioselectivity of the addition of HO-acids to the activated π bond in N,N-bis(oxy)enamines has been found to be dramatically dependent upon the solvent. Mechanistic investigations and quantum-chemical calculations revealed that solvent affects the reaction pathway. In basic solvents (DMF, NMP, DMSO), N,N-bis(oxy)enamines were converted into nitrosoalkenes by a Lewis base promoted process followed by oxy-Michael addition of the HO-acid. In non-polar solvents (toluene, CH2Cl2), the reaction occurs by an acid-promoted SN′ substitution of the N-oxy-group via a highly reactive N-vinyl-N-alkoxynitrenium species. Based on these studies, general and efficient protocols for the oximinoalkylation of various HO-acids (carboxylic acids, phenols, hydroxamic, phosphoric and sulfonic acids) employing readily available N,N-bis(oxy)enamines were developed. These methods proved to be applicable to the post-modification of natural molecules bearing acidic OH groups (such as steroidal hormones, bile acids, protected amino acids and peptides) and ligands (BINOL). The resulting α-oxyoximes were demonstrated to be useful precursors of valuable 1,2-amino alcohol or 1,2-hydroxylamino alcohol derivatives, including the antiarrhythmic drug Mexiletine and a potent matrix metalloproteinase inhibitor.
Cycloaddition reactions of nitrosoalkenes, azoalkenes and nitrile oxides mediated by hydrotalcite
Lemos, Americo,Lourenco, Joao P.
scheme or table, p. 170 - 182 (2010/08/20)
Mg:Al 3:1 hydrotalcite (Ht), used in catalytic quantities, promotes the generation of nitrosoalkenes, azoalkenes and nitrile oxides. These can be intercepted in situ by heterocycles and olefins in [4+2] and [3+2] cycloaddition reactions, producing dihydro
Hydrotalcite catalysed [4+2] cycloaddition reactions of nitroso- and azo-alkenes
Lemos, Américo,Louren?o, Jo?o Paulo
experimental part, p. 1311 - 1313 (2009/07/17)
The generation of nitroso- and azo-alkenes and their [4+2] cycloaddition reactions with furan and ethyl vinyl ether, producing dihydro-1,2-oxazines and tetrahydropyridazines, by the use of catalytic Mg:Al 3:1 hydrotalcite, is described. The absence of an
A new strategy for the stereoselective synthesis of unnatural α-amino acids
Gallos, John K.,Sarli, Vassiliki C.,Massen, Zoe S.,Varvogli, Anastassia C.,Papadoyanni, Constantina Z.,Papaspyrou, Sofia D.,Argyropoulos, Nicolaos G.
, p. 565 - 574 (2007/10/03)
A new method for the synthesis of racemic non-proteinogenic α-amino acids has been developed, which involves (i) hetero-Diels-Alder addition of ethyl 2-nitrosoacrylate to electron rich alkenes such as enol ethers, enamines and allylsilanes, (ii) NaCNBH3 reduction of the CN bond in the oxazines thus generated, the stereochemistry of the products being controlled by epimerisation of the thermodynamically less stable isomer to the more stable one, (iii) protection of the N-H group as N-Boc and (iv) finally, N-O bond cleavage of both free and protected products to give proline or bis-homoserine derivatives, respectively. An example with concomitant reduction of the carboxylate group, resulting in the formation of the respective amino alcohol is reported. Applying this methodology to a homochiral enol ether, the protected parent d-proline was prepared in enantiomerically pure form, whereas the asymmetric synthesis of the respective bis-homoserine was unsuccessful. Graphical Abstract.
The hetero-Diels-Alder addition of ethyl 2-nitrosoacrylate to electron-rich alkenes as a route to unnatural α-amino acids
Gallos, John K.,Sarli, Vassiliki C.,Varvogli, Anastassia C.,Papadoyanni, Constantina Z.,Papaspyrou, Sofia D.,Argyropoulos, Nicolaos G.
, p. 3905 - 3909 (2007/10/03)
A new method for the stereoselective synthesis of nonproteinogenic α-amino acids has been developed, which involves hetero-Diels-Alder addition of ethyl 2-nitrosoacrylate to electron-rich alkenes, such as enol ethers, enamines and allylsilanes, and a furt
Reduction of Ethyl 5,6-Dihydro-4H-1,2-oxazine-3-carboxylates. A Route to Proline Ethyl Ester and Other Ethyl Pyrrolidine-2-carboxylates
Chrystal, Ewan J. T.,Gilchrist, Thomas L.,Stretch, Wayne
, p. 1563 - 1576 (2007/10/02)
The title dihydro-oxazines, which are formed by cycloaddition of ethyl 2-nitrosopropenoate to nucleophilic alkenes, are reductively cleaved by reaction with aluminium amalgam and by hydrogenation over palladium in the presence of triethyl borate.The produ
