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Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic Chemistry
Volume 17, 1987 - Issue 6
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Original Articles

An Improved Procedure for Diazotization Fluoro-Dediazoniation of Anilines Using Organic Base-HF Agents

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Pages 685-692 | Published online: 19 Dec 2006

References

  • Zollinger , H. 1961 . “ Azo and Diazo chemistry, Aliphatic and Aromatic Compounds ” . New York : Interscience . H. Suschizky, Adv. Fluorine Chem., 4, 1(1965); C. G. Swain and R. Randall, J. Am. Chem. Soc., 97, 799(1975); H. Nakazumi, I. Szele, K. Yoshida and H. Zollinger, Helv. Chim. Acta 66, 1721(1983).
  • Flood , D. T. 1943 . Org. Synth., Coll. II , : 295
  • Ferm , R. L. and Werf , C. V. 1950 . J. Am. Chem. Soc. , 72 : 4809 S. Misaki, Japan Patent 49-81330 (1974), ibid 53-14057 (1978); M. M. Boudakian, U. S. Patent 4096196 (1978).
  • Olah , G. A. , Welch , J. T. , Vankar , Y. D. , Nojima , M. , Kerekes , I. and Olah , J. A. 1979 . J. Org. Chem. , 44 : 3872
  • None of the anilines were detected after quenching the solution at this step.
  • The relationship between pyridine concentraion (wt%) in pyridine-HF solution and temperature are as follows: 30% pyridine/55° C; 40% pyridine/90° C; 43% pyridine/150° C.
  • It should be noted that anilines must be protonated before the addition of NaNO2 to the mixture of organic base-HF and anilines, otherwise, undesirable reactions may occur to form tarry substances. For example, aniline gives fluorobenzene in only 40-60% yield at the dediazoniation temperature of 55° C using 30% pyridine-HF when the protonation step of aniline is carried out insufficiently.
  • Fukuhara , T. , Sawada , T. , Yoneda , N. and Suzuki , A. Oct. 1985 . 10th Fluorine Chemistry Symposium Kanazawa Abstr., No. 2G2-01
  • Olah and his co-workers reported meta-NO2-, para-NO2-, ortho-CF3- and meta-CF3- anilines gave the fluoroarene in yields of 35, 45, 50 and 46% respectively which were contained in a mixture of isomers in the reaction using Olah's reagent (30 wt% pyridine-HF) and NaNO2.4)
  • By the reaction of one mole of aniline, two moles of HF are consumed and two moles of H2O are formed. The HF-H2O solution which is free of volatile HF at 55° C was found to have three molar ratio of HF/H2O. Thus, the requisite amount of fresh HF was determined to be 8-fold moles of aniline charged in each run.

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