Smiles rearrangement as a tool for the preparation of 5-[(2-hydroxyacyl)amino]-2,4,6-triiodo-1,3-benzenedicarboxamides: Main pathway and side reactions

Tetrahedron

Volumn 53, Issue 34, 1997, Pages 11919-11928

  Anelli, Pier Lucio ^a   Brocchetta, Marino ^a   Calabi, Luisella ^a   Secchi, Carlo ^a   Uggeri, Fulvio ^a   Verona, Sandra ^a  

^a Milano Research Centre   (Italy)

Author keywords

[No Author keywords available]

Indexed keywords

AMIDE;

ARTICLE; CYCLIZATION; DRUG SYNTHESIS; HIGH PERFORMANCE LIQUID CHROMATOGRAPHY; IN VITRO STUDY; MASS SPECTROMETRY; NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY; PRIORITY JOURNAL; REACTION ANALYSIS; STEREOCHEMISTRY; THERMODYNAMICS;

EID: 0030877159     PISSN: 00404020     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0040-4020(97)00764-3     Document Type: Article

References (26)

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18. Although substoichiometric amounts of base can be used successfully for the rearrangement of secondary phenoxyacetamides, with primary phenoxyacetamides the use of 1 mol equiv of base is required because the rearranged anilides are salified.
19. 14 lacking the three iodine atoms, either does not rearrange under basic conditions even at high temperature and under long reaction times (method B) or hydrolyses to the corresponding phenoxyacetic acid without rearrangement (method A).
20. 7a starting from 2,4,6-triiodophenol and N,N′-bis(2,3-dihydroxypropyl)-5-hydroxy-1,3-benzenedicarboxamide, respectively.
21. While with substrates 2a,b (method B only) the equilibrium 2 ↔ 1 is fully shifted to the right due to salification of the anilidic NH, with substrates 2c-f both methods lead to mixtures of 2 and 1 which mainly contain rearranged products 1c-f. For each substrate the composition of such a mixture, being solvent dependent, is slightly different for the two methods. The higher content of rearranged product in the equilibrium mixtures derived from 2c,d, compared to those derived from 2e,f, could be related to the minor steric hindrance of the methyl group compared to that of the hydroxyalkyl groups.
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24. The presence of β-and γ-OH in N-alkyl residues of secondary and tertiary phenoxyacetamides noticeably accelerates the cleavage of the amide bond in water, even at neutral pH. See Anelli, P. L.; Brocchetta, M.; Canipari S.; Losi P.; Manfredi, G.; Tomba C.; Zecchi, G. Gazz. Chim. Ital. 1997, 127, in press.
25. As expected on the basis of the results described for 2c,d, method B, after 2.5 h, led to the formation of benzoxazinone 4h, which was characterized after deprotection to 4g.
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