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Synlett 2003(6): 0879-0881
DOI: 10.1055/s-2003-38746
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Electron Deficient Dienes. 4. [1] A Synthetic Equivalent of 4-Methylene­glutaconic Acid, its Mono and Diethyl Esters and their Use in a Concise General Synthesis of Isophthalic Acids and Isophthalates

Graham J. Bodwell*, Krista M. Hawco, Teizi Satou
Chemistry Department, Memorial University of Newfoundland, St. John’s, NL, A1B 3X7, Canada
Fax: +1(709)7373702; e-Mail: gbodwell@mun.ca;
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Publication History

Received 17 March 2002
Publication Date:
17 April 2003 (online)

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Abstract

Reaction of a series of 2′-hydroxybenzophenone-3-carboxylic acid ethyl esters under Dakin reaction conditions affords isophthalic acid monoethyl esters, which can be converted into the corresponding diethyl isophthalates (6 examples) and isophthalic acid (1 example) by esterification and hydrolysis, respectively. This transformation renders the direct precursor of the benzophenones a synthetic equivalent of 4-methyleneglutaconic acid (4-methylenepent-2-enedioic acid) and its mono and diethyl esters.

Key words

Dakin reaction - Diels-Alder - inverse electron demand - isophthalates - isophthalic acids

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Bodwell, G. J.; Hawco, K. M. unpublished results.

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Sample Procedure: 4,6-Indandicarboxylate Diethyl Ester ( 4): [9] [10] To a stirred suspension of NaH (60% dispersion in mineral oil, 35.2 mg, 0.88 mmol) in THF (15 mL) was added dropwise a solution of 11 (219.5 mg, 0.71 mmol) in THF (5 mL) and the resulting yellow solution was stirred for 10 min. To the resulting solution was added H2O2 (30% aq solution, 95.3 mg, 0.84 mmol) and the mixture was stirred for 20 h. The reaction mixture was concentrated under reduced pressure, and concentrated aq HCl solution (5 mL) was added. The resulting precipitate was collected by suction filtration and washed with a small amount of H2O. The solid was dried in vacuo and then suspended in absolute EtOH (25 mL). To this suspension was added concentrated H2SO4 (0.5 mL) and the mixture was heated at reflux for 11 h. The solvent was removed under reduced pressure and H2O (25 mL) was added. The mixture was then extracted with CH2Cl2 (3 × 25 mL). The combined organic layers were washed with sat. aq NaHCO3 solution, and dried over MgSO4. The solvent was removed under reduced pressure and the residue was subjected to silica gel column chromatography (20% EtOAc/hexane) to afford diester 4 (144.2 mg, 78%) as pale yellow crystals: Mp 43-45 °C. 1H NMR (500 MHz, CDCl3): δ = 8.49 (s, 1 H), 8.04 (s, 1 H), 4.390 (q, J = 7.2 Hz, 2 H), 4.384 (q, J = 7.1 Hz, 2 H), 3.32 (t, J = 7.4 Hz, 2 H), 2.97 (t, J = 7.4 Hz, 2 H), 2.13 (quint, J = 7.4 Hz, 4 H), 1.411 (t, J = 7.2 Hz, 3 H), 1.407 (t, J = 7.5 Hz, 2 H). 13C NMR (125 MHz, CDCl3): δ = 166.7, 166.5, 152.1, 146.6, 129.9, 129.1, 127.1, 61.3, 61.1, 34.3, 32.5, 25.2, 2 × 14.6. IR(nujol): ν = 1724 (s), 1299 (m), 1227 (s)cm-1. UV/Vis (CH2Cl2): λmax (log ε) = 302 (3.38) nm; MS (EI. 70 eV): m/z (%) = 262 (69) [M+], 233 (100), 117 (99). HRMS (EI): m/z calcd for C15H18O4 [M+]: 262.1205. Found: 262.1223. All other products were characterized as above.