Direct oxidative cascade cyclisation of 2-aminobenzoic acid and arylaldehydes to aryl 4H-3,1-benzoxazin-4-ones with oxone (original) (raw)
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The Journal of Organic Chemistry, 2006
[1,4]oxazine derivatives (3 and 5, respectively) were synthesized for the first time starting from readily available 2-prop-2-ynyloxyphenols 1 and 2-prop-2-ynyloxyanilines 4, respectively, through tandem oxidative aminocarbonylation of the triple bondsintramolecular conjugate addition. Reactions were carried out in the presence of catalytic amounts of PdI 2 in conjunction with an excess of KI in N,N-dimethylacetamide (DMA) as the solvent at 80-100°C and under 20 atm (at 25°C) of a 4:1 mixture of CO-air. The reaction showed a significant degree of stereoselectivity, the Z isomers being formed preferentially or exclusively. The configuration around the double bond of the major stereoisomers was unequivocally established by X-ray diffraction analysis.
Novel 1,4-benzoxazine derivatives were synthesized by an efficient and simple method in high yields. Readily available starting materials, operational simplicity, mild reaction conditions and novelty are the key advantages of this method. The synthetically attractive feature of the procedure is reflected by its applicability to a wide range of isatin and aniline derivatives. Besides their novel structures, these compounds may have important biological activities and industrial applications. Furthermore, we demonstrated that in BaeyereVilliger oxidation reaction, the phenyl group migrate better than amidine groups but not as good as amide group. The migratory ability for these groups in BaeyereVilliger oxidation reaction is ranked amide > phenyl > amidine.
One-Step Synthesis of Oxazoline and Dihydrooxazine Libraries
Journal of Combinatorial Chemistry, 2007
Oxazolines appear in numerous medicinally active compounds and natural products of biological significance. 1 Additionally, they are valuable as synthetic intermediates or protecting groups 2 in organic synthesis, 3 and commonly appear in ligands for asymmetric synthesis ). 4 The most common mode of oxazoline synthesis involves preparation of a β-hydroxy amide followed by cyclization. Typical cyclization reagents include Burgess reagent, 5 PPh 3 /DIAD, 6 DIC/Cu(OTf) 2 ,7 molybdenum oxide, 8 and DAST/Deoxo-Fluor. 9 The six-membered homologous dihydrooxazines have been prepared by various methods that include [4+2] cycloadditions between N-acyl imines and alkenes, 10 1,4-dipolar cycloaddition reactions between olefins and aminomethyl ions, 11 and from stereochemically defined Nthioacyl-1,3-amino alcohols in the presence of Bu 4 NF and EtI. 12
New Approach for the Synthesis of Aryloxy 1,3-OXAZINES
International Journal of Research -GRANTHAALAYAH, 2020
Oxazine compounds have drew the attention of many researchers to find different approaches to the synthesis of this type of compounds according to the success of their use in a wide range of pharmaceutical application during the last decades .It is also for the difference reactivity of these analogues is exhaustively depicted and illustrates the rich versatility of this class of starting material. They proved to have most of actions of a combination of other drugs. We are herein investigate the synthesis of ethyl aryloxy acetate(S1-6) from the reaction of the corresponding ethyl bromo acetate with aryl phenols .These intermediates were cyclized with antharanilic acid affording the titled compounds
Zeitschrift für Naturforschung B, 2008
New model 1,2,4-triazino[6,5-h]quinolines 8a-c are prepared by oxidative cyclization of the respective N-(quinolin-8-yl)amidrazone precursors 7a-c using copper(II) chloride. Interestingly, the cyclized products 8a-c were found to be arylated at N1 position. Analytical and spectral (MS, NMR) data of the title products are in compliance with the allocated structures.
ChemInform, 2011
The laccase-catalyzed domino reaction of o-phenylenediamine and benzaldehydes with aerial oxygen as the oxidant exclusively yields 2-aryl-1H-benzimidazoles in good to very good yields. It is easy to perform under very mild reaction conditions. Laccases are multicopper oxidases which are able to catalyze the selective oxidation of a number of substrates using oxygen as an oxidant under mild reaction conditions. The oxidation of the substrate is accompanied by the reduction of oxygen to give water as the only side product. 1 Over the last few years the interest in laccase-catalyzed transformations has increased. 2 It has been demonstrated that laccases can be used for the oxidation of aromatic methyl groups, 3a benzylic, allylic, and aliphatic alcohols, 3b ethers, 3c benzyl amines and hydroxylamines. 3d Laccases have also been employed for the oxidation of catechols and hydroquinones to the corresponding benzoquinones and related transformations. 4 Also, there is ample evidence that laccases catalyze the oxidative coupling of several phenolics using oxygen as the oxidant. 5 In a number of contributions we have reported that laccase initiated domino reactions between catechols and several 1,3-dicarbonyls can be employed for the synthesis of a number of heterocyclic systems, including 1H-pyrano[4,3-b]benzofuran-1-ones, 6b,c 3,4-dihydrodibenzofuran-1(2H)-ones, 6b and benzofuro[3,2-c]pyridin-1(2H)ones. 6a As part of our studies of the laccase-catalyzed domino processes we have observed that the oxidative transformation of o-phenylenediamine (1a) with air as the oxidant in the presence of catalytic amounts of laccase from Agaricus bisporus exclusively delivers 2,3diaminophenazine (2) in 90% yield (Scheme 1).
Catalytic Oxidative Cyclocondensation of o ‐Aminophenols to 2‐Amino‐3 H ‐phenoxazin‐3‐ones
Synthetic Communications, 2007
The catalytic oxidative cyclocondensation of the o-aminophenols 1a -f was investigated. The oxidants used were air/laccase, H 2 O 2 /horseradish peroxidase, H 2 O 2 /ebselen (3), and TBHP/diphenyl diselenide 4. The products obtained were 2-amino-3H-phenoxazin-3-one-questiomycin A, its derivative 2b, and cinnabarinic acid and actinocin (2c,d). Substrates with methyl groups at 4 and 5 positions of benzene ring were converted to different dihydrophenoxazinones 2g,h. Compounds having chlorine atoms at the same positions underwent oxidation to planar phenoxazinones 2e,f with elimination of one hydrochloride molecule.