Mechanism of Polyphosphoric Acid and Phosphorus Pentoxide-Methanesulfonic Acid as Synthetic Reagents for Benzoxazole Formation

Journal of Organic Chemistry

Volumn 62, Issue 11, 1997, Pages 3552-3561

  So, Ying Hung ^a   Heeschen, Jerry P ^a  

^a DOW CHEMICAL COMPANY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000894153     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo960441u     Document Type: Article

References (32)

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19. 5 in sulfuric acid at 50 °C for 4 h, no 2-hydroxybenzanilide nor 2-phenylbenzoxazole was formed.
20. (a) Phosphorus-31 NMR, Principles and Applications; Gorenstein, D. G., Ed.; Academic Press: New York, 1984.
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22. Percentages are wt % unless specified.
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24. A detailed description of this part has been published; see: So, Y. H.; Heeschen, J. P.; Murlick, C. L. Marcomolecules 1995, 28, 7289-7290.
25. Imai and co-workers proposed esters as the intermediates for polybenzoxazole and polybenzothiazole formation based on the observation that high molecular weight polybenzoxazole and polybenzothiazole were prepared much faster than the corresponding polybenzimidazole; see: Imai, J.; Taoka, I.; Uno, K.; Iwakura, J. Makromol. Chem. 1965, 83, 167-178.
26. Raiford, L. C.; Couture, J. R. J. Am. Chem. Soc. 1924, 46, 2305-2318.
27. In the reaction of benzoyl chloride and o-aminophenol in PPA, 2-benzamidophenyl benzoate and 2-hydroxybenzanilide were isolated. The result suggests direct amide formation from o-aminophenol and benzoyl chloride is possible.
28. 5-MSA or PPA-MSA was used as the reagent for 2-phenylbenzoxazole synthesis from benzole acid and o-aminophenol, both 2-hydroxybenzanilide and 2-methanesulfonamidophenyl benzoate were isolated as reaction intermediates.
29. Standard Test Method 01-04-01, Polyphosphoric Acid Assay by Chain Length Determination; Stauffer Chemical Co., Basic Products Group, May 30, 1984.
30. 13C NMR spectra signal peaks were assigned with the following references: (a) Reference 19. (b) Kalinowski, H.-A.; Berger, S.; Braun, S. Carbon-13 NMR Spectroscopy; Wiley: New York, 1988.
31. 13C NMR spectra signal peaks were assigned with the following references: (a) Reference 19. (b) Kalinowski, H.-A.; Berger, S.; Braun, S. Carbon-13 NMR Spectroscopy; Wiley: New York, 1988.
32. 13C NMR spectrum for protonated aniline were based on (c) 6822C which are different from assignments in (b) p 315.