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Synlett 2002(4): 0573-0574
DOI: 10.1055/s-2002-22710
LETTER
© Georg Thieme Verlag Stuttgart · New York

The Efficient Allylations of 2-Oxocarboxylic Acids. Synthesis of 2-Allyl Derivatives of 2-Hydroxycarboxylic Acids

Subodh Kumar*, Pervinder Kaur, Swapandeep Singh Chimni
Department of Chemistry, Guru Nanak Dev University, Amritsar -143 005, India
e-Mail: subodh.kumar@angelfire.com;
Further Information

Publication History

Received 11 February 2001
Publication Date:
05 February 2007 (online)

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Abstract

2-Oxocarboxylic acids or their sodium salts undergo indium-mediated allylation with allyl bromide cinnamyl bromide and ethyl 4- bromocrotonate to provide the corresponding 2-allyl derivatives of glycolic lactic mandelic and malic acids. In the case of reactions with cinnamyl bromide or ethyl 4-bromocrotonate high diastereoselectivity is achieved.

Key words

allylation reactions - hydroxycarboxylic acids - diastereoselective

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General Procedure: The 2-oxocarboxylic acid 1 (0.5 mmol), allyl bromide (0.75 mmol), indium metal (0.5 mmol) were taken in THF-H2O (2:1) mixture and the reaction mixture was stirred at 30 °C until the indium metal dissolved. The turbid reaction mixture was treated with dilute HCl and extracted with CHCl3. The solvent was distilled off and the residue was column chromatographed (silica gel, 60-120 mesh) to isolate the allyl addition product. In the case of reactions with sodium 2-oxocarboxylate (0.5 mmol), 2 C (1.5 mmol) and indium (1.0 mmol) the pH (4.7) of the reaction was controlled initially by addition of HOAc and during the course of reaction with aq NaOH (2%).

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1 H NMR spectral data for the representative cases are given here. 3e: δ 2.18 (s,1 H, OH, exchanges with D2O), 3.86 (dd, J 1 = 7.6 Hz, J 2 = 4 Hz, 1 H, CH), 4.59 (d, J = 4 Hz, 1 H, CH), 5.20-5.29 (m, 2 H, =CH2), 6.17-6.32 (m, 1 H, =CH), 7.22-7.37 (m, 5 H, ArH) (For Na salt: mp >300 °C, found C 61.4; H 5.1%. C11 H11O3Na requires C 61.7; H 5.1%). 3f: mp 168 °C; δ 4.39 (s, 1 H, OH, exchanges with D2O), 4.4 (d,
J = 9.5 Hz, 1 H, CH), 4.79-4.99 (m, 2 H, =CH2), 5.89-6.03 (m, 1 H, =CH), 7.19-7.41 (m, 8 H, ArH), 7.72-7.73 (m, 2 H, ArH) (Found C 76.3; H 5.99%. C17H16O3 requires C 76.1; H 5.97%). 3g : δ 1.31 (t, J = 7 Hz, 3 H, CH3), 2.09 (s, 1 H, OH, exchanges with D2O), 3.62 (dd, J 1 = 8.4 Hz, J 2 = 3.6 Hz,
1 H, CH), 4.20 (s, 1 H, OH, exchanges with D2O), 4.22 (q,
J = 7 Hz, 2 H, OCH2) 4.47 (d, J = 3.6 Hz, 1 H, CH), 5.26-5.38 (m, 2 H, =CH2), 5.77-6.07 (m, 1 H, =CH) (For Na salt: mp >300 °C; found C 45.4, H 4.9. C8H11O5Na requires C 45.7; H, 5.2%). 3 h: mp 97-98 °C; δ 1.29 (t, J = 7.2 Hz,
3 H,CH3), 2.20 (s, 1 H, OH, exchanges with D2O), 4.14 (d,
J = 8.2 Hz, 1 H, CH), 4.22 (q, J = 7.2 Hz, 2 H, OCH2), 5.02-5.17 (m, 2 H, =CH2), 5.56-5.68 (m, 1 H, =CH), 7.29-7.42 (m, 8 H, ArH), 7.58-7.63 (m, 2 H, ArH). (Found C 63.3;
H 6.0%. C14 H16O5 requires C 63.3; H 6.06%).

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Similar increase in both rate of reaction and diastereoselectivity of allylation at pH 4.0 and slowed allylation at pH 7.0 was reported earlier (ref. [2d] ).