- Metal-free syntheses of oxazoles and their analogues based on λ3-iodane-mediated cycloisomerization/functionalization reactions or [2+2+1] cycloaddition type reactions
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As a metal-free construction of oxazoles and furans concomitant with the introduction of oxygen functional groups or fluorine atoms into the side chains, we have developed λ3-iodane-mediated cycloisomerization/functionalization reactions of propargyl compounds. In these reactions, aryl- λ3-iodane ArI(X)Y works not only as a donor of heteroatomic functional groups but also as an activator of carbon-carbon triple bonds. Therefore, this methodology is not required any transition metal catalysts, which are frequently used in previous methods. Furthermore, this methodology can be extended to λ3-iodane-mediated [2+2+1] cycloaddition type reactions of alkynes, nitriles and heteroatoms for metal-free formation of oxazoles and imidazoles.
- Saito, Akio
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- Synthesis of Extended Oxazoles III: Reactions of 2-(Phenylsulfonyl)methyl-4,5-diaryloxazoles
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2-((Phenylsulfonyl)methyl)-4,5-diphenyloxazole is a useful scaffold for synthetic elaboration at the 2-methylene position thereby affording extended oxazoles. The corresponding α-sulfonyl anion reacts smoothly with diverse alkyl halides giving monoalkylated (47-90%), dialkylated (50-97%), and cyclic (59-93%) products. The reductive desulfonylation of the monoalkylated and selected dialkylated products was optimized with a magnesium/mercuric chloride reagent system and afforded desulfonylated products in the range of 66-97%. The anti-inflammatory Oxaprozin was prepared using the α-sulfonyl carbanion strategy along with optimized desulfonylation.
- Patil, Pravin C.,Luzzio, Frederick A.
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p. 10521 - 10526
(2016/11/17)
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- Catalytic transformation of esters of 1,2-azido alcohols into α-amido ketones
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The esters of 1,2-azido alcohols were transformed into α-amido ketones without external oxidants through the Ru-catalyzed formation of N-H imines with the liberation of N2 followed by intramolecular migration of the acyl moiety. A wide range of α-amido ketones were obtained, and one-pot transformation into the corresponding oxazoles (or a thiazole) was demonstrated.
- Kim, Yongjin,Pak, Han Kyu,Rhee, Young Ho,Park, Jaiwook
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supporting information
p. 6549 - 6552
(2016/06/01)
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- Synthesis of extended oxazoles II: Reaction manifold of 2-(halomethyl)-4,5-diaryloxazoles
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2-(Halomethyl)-4,5-diphenyloxazoles are effective, reactive scaffolds which can be utilized for synthetic elaboration at the 2-position. Through substitution reactions, the chloromethyl analogue is used to prepare a number of 2-alkylamino-, 2-alkylthio-, and 2-alkoxy-(methyl) oxazoles. The 2-bromomethyl analogue offers a more reactive alternative to the chloromethyl compounds and is useful in the C-alkylation of a stabilized (malonate) carbanion as exemplified by a concise synthesis of Oxaprozin.
- Patil, Pravin C.,Luzzio, Frederick A.
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supporting information
p. 757 - 759
(2016/02/05)
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- One-pot preparation of 2,5-disubstituted and 2,4,5-trisubstituted oxazoles from aromatic ketones with molecular iodine, oxone, and trifluoromethanesulfonic acid in nitriles
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Alkyl aryl ketones were successfully converted into the corresponding 2,5-disubstituted and 2,4,5-trisubstituted oxazoles in good to moderate yields in a one-pot manner, utilizing iodine, Oxone, and trifluoromethanesulfonic acid in nitriles under transition-metal-free conditions. The present method could be used for the preparation of Oxaprozin from benzyl phenyl ketone and succinonitrile. A possible reaction mechanism was proposed in which the key intermediates were α-iodoalkyl aryl ketones and α-iodosylalkyl aryl ketones.
- Imai, Sho,Kikui, Hiroki,Moriyama, Katsuhiko,Togo, Hideo
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p. 5267 - 5274
(2015/07/15)
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- Metal-free [2 + 2 + 1] annulation of alkynes, nitriles, and oxygen atoms: Iodine(III)-mediated synthesis of highly substituted oxazoles
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The metal-free [2 + 2 + 1] annulation of alkynes, nitriles, and O-atoms for the regioselective assembly of 2,4-disubstituted and 2,4,5-trisubstituted oxazole compounds has been achieved by the use of PhIO with TfOH or Tf 2NH. The present reaction could be applied to a facile synthesis of an anti-inflammatory drug.
- Saito, Akio,Taniguchi, Akihiro,Kambara, Yui,Hanzawa, Yuji
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supporting information
p. 2672 - 2675
(2013/07/19)
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- Synthesis, characterization and antiproliferative activity of transition metal complexes with 3-(4,5-diphenyl-1,3-oxazol-2-yl)propanoic acid (oxaprozin)
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A series of novel Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes with oxaprozin (Hoxa), a non-steroidal anti-inflammatory drug, has been synthesized. The drug and complexes have been characterized by elemental and thermogravimetric (TG) analysis, Fourier transform (FT)-IR, 1H-NMR, 13C-NMR, UV-Vis spectroscopy and magnetic susceptibility measurements. The (pseudo)octahedral geometry has been proposed for all complexes based on electronic spectra and magnetic moments. With exception of the Cu(II) complex, where bridging bidentate mode of COO groups has been found, FT-IR spectra confirmed chelately coordinated COO groups in the other complexes. The general formula of the complexes is [M(H2O)2(oxa) 2] · xH2O, with x=2 for M=Mn, Co and Ni and x=1.5 for Zn. The binuclear Cu(II) complex, [Cu2(H2O) 2(OH)(oxa)3]·2H2O, has strong Cu-Cu interactions of antiferromagnetic type. The complexes and Hoxa did not exhibit the cytotoxic effect to peritoneal macrophages. For the first time these complexes have been tested for their in vitro antiproliferative activity against human colon and breast cancer cell lines, HCT-116 and MDA-231, respectively. For all investigated compounds significant antiproliferative effects have been observed. Ni(II) complex has been shown to be a promising antiproliferative agent exerting excellent activity against HCT-116 even in nanomolar concentrations.
- Bozic, Bojan D.J.,Rogan, Jelena R.,Poleti, Dejan D.,Trisovic, Nemanja P.,Bozic, Biljana D.J.,Uscumlic, Gordana S.
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scheme or table
p. 865 - 869
(2012/09/21)
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- Synthesis of oxazoles from enamides via phenyliodine diacetate-mediated intramolecular oxidative cyclization
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A group of functionalized oxazoles were synthesized in moderate to good yields from enamides via phenyliodine diacetate (PIDA)-mediated intramolecular cyclization. The main advantageous features of the present method include its broad substrate scope and the heavy-metal-free characteristic of the oxidative carbon-oxygen bond formation process.
- Zheng, Yunhui,Li, Xuming,Ren, Chengfeng,Zhang-Negrerie, Daisy,Du, Yunfei,Zhao, Kang
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p. 10353 - 10361
(2013/01/15)
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- Synthesis of Oxazoles by the Reaction of Ketones with Iron(III) Solvates of Nitriles
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Oxazoles having functionalized carbon substituents at the C-2 position were synthesized in one step by the oxidation of ketones with iron(III) solvates of nitriles, i.e., Fe(RCN)6(ClO4)3(solvate A) or Fe(RCN)6)FeCl4)3(solvate B), in the corresponding nitriles.Keywords oxazole; ketone; oxidation; nitrile; iron(III) nitrile solvate
- Kotani, Eiichi,Kobayashi, Shigeki,Adachi, Mayumi,Tsujioka, Toshiyuki,Nakamura, Kouji,Tobinaga, Seisho
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p. 606 - 609
(2007/10/02)
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- Process for preparing oxazoles
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(4,5-Diaryloxazol-2-yl)propionic and butyric acids having anti-inflammatory activity had previously been prepared by esterification of aroylarylcarbinols with a reactive derivative of butanedioic and pentanedioic acids, for instance, succinic or glutaric anhydride, isolation of the keto ester so formed and cyclization of the keto ester with a nitrogen-donating cyclizing agent, for instance, ammonium acetate in acetic acid. It has now been found that the omission of the isolation of the keto ester intermediate improves the purity of the oxazole product.
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