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Synlett 2007(2): 0288-0292  
DOI: 10.1055/s-2007-967985
LETTER
© Georg Thieme Verlag Stuttgart · New York

An Efficient DABCO-Catalyzed Ireland-Claisen Rearrangement of Allylic Acrylates

Yunxia Lia, Quanrui Wang*a, Andreas Goekeb,c, Georg Fráter*c
a Department of Chemistry, Fudan University, 200433 Shanghai, P. R. of China
Fax: +86(21)65641740; e-Mail: qrwang@fudan.edu.cn;
b Shanghai Givaudan Ltd., Fragrances, 201203 Shanghai, P. R. of China
c Givaudan Schweiz AG, Fragrance Research, Überlandstraβe 138, 8600 Dübendorf, Switzerland
Fax: +41(44)8242926; e-Mail: georg.frater@givaudan.com;
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Publikationsverlauf

Received 17 October 2006
Publikationsdatum:
24. Januar 2007 (online)

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Abstract

A novel DABCO-catalyzed Ireland-Claisen [3,3]-rearrangement of allylic acrylates to give α-methylene-γ,δ-unsaturated carboxylic acids in the presence of an excess of TMSCl and DBU in refluxing acetonitrile was developed. The protocol provides an easy entry to α-methylene-γ,δ-unsaturated carboxylic acids from ­allylic alcohols in good yields.

Key words

DABCO - allylic acrylates - Ireland-Claisen rearrangement - α-methylene-γ,δ-unsaturated carboxylic acids

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General Procedure of the Rearrangement.
A reaction flask was charged with the allylic acrylate 3 (32.4 mmol), DABCO (0.73 g, 6.5 mmol), TMSCl (10.58 g, 97.4 mmol), DBU (9.90 g, 65.0 mmol) and MeCN (75 mL). The mixture was heated under reflux and the reaction was monitored by GC or TLC until the reaction was complete (reaction time as specified in Table [1] ). Then, the volatiles were removed under reduced pressure. The residue was suspended in Et2O (100 mL) and stirred with 3 N HCl (40 mL) for a couple of minutes. The organic layer was separated, and washed sequentially with brine and H2O, dried over anhyd MgSO4 and concentrated in vacuo. The residue was purified by column chromatography or subjected to bulb-to-bulb distillation or recrystallization from EtOH to afford the pure compounds 4a-h as a colorless oil and 4i-j as a white solid (Table [1] ).

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All new compounds have been isolated in pure form and characterized by spectral data (NMR, IR and MS).
Selected Data for Compounds 4.
Compound 4c: 1H NMR (300 MHz, CDCl3): δ = 12.23 (br, 1 H), 6.33 (s, 1 H), 5.67 (br s, 1 H), 5.52 (dd, J = 15.5, 6.1 Hz, 1 H), 5.42 (dt, J = 15.5, 6.1 Hz, 1 H), 2.99 (d, J = 6.1 Hz, 2 H), 2.30 (dsept, J = 6.1, 6.8 Hz, 1 H), 1.00 (2 d, J = 6.8 Hz, 6 H). 13C NMR (75 MHz, CDCl3): δ = 173.0 (s), 140.5 (d), 139.5 (s), 127.3 (t), 123.0 (d), 34.1 (t), 31.1 (d), 22.4 (2q). IR (KBr): ca. 3000, 1698, 1436, 1289, 1158, 952 cm-1. MS (EI): m/z = 154 [M]+, 111 [M - C3H7]+.
Compound 4e: 1H NMR (300 MHz, CDCl3): δ = ca. 11.1 (br, 1 H), 6.32 (s, 1 H), 5.68 (s, 1 H), 5.15 (t, J = 7.2 Hz, 1 H), 3.03 (d, J = 7.2 Hz, 2 H), 2.08 (br q, J = 7.5 Hz, 2 H), 2.07 (q, J = 7.5 Hz, 2 H), 1.03 (t, J = 7.5 Hz, 3 H), 0.97 (t, J = 7.5 Hz, 3 H). 13C NMR (75 MHz, CDCl3): δ = 173.1 (s), 145.6 (s), 139.5 (s), 126.9 (t), 118.2 (d), 29.2 (2 t), 23.2 (t), 12.1 (q), 12.8 (q). IR (KBr): ca. 3000, 1698, 1629, 1434, 1283, 1155, 954 cm-1. MS (EI): m/z = 168 [M]+, 139 [M - C2H5]+.
Compound 4f (major trans-isomer): 1H NMR (300 MHz, CDCl3): δ = ca. 11.0 (br, 1 H), 6.31 (s, 1 H), 5.65 (s, 1 H), 5.23 (t, J = 7.2 Hz, 1 H), 3.01 (d, J = 7.2 Hz, 2 H), 2.30 (sept, J = 6.8 Hz, 1 H), 1.60 (s, 3 H), 1.03 (2 d, J = 6.8 Hz, 6 H). 13C NMR (75 MHz, CDCl3): δ = 173.1 (s), 144.1 (s), 139.1 (s), 126.8 (t), 117.6 (d), 36.8 (d), 29.4 (t), 21.4 (2q), 13.3 (q). IR (KBr,): ca. 3000, 1695, 1630, 1434, 1284, 1156, 952
cm-1. MS (EI): m/z = 168 [M]+, 125 [M - C3H7]+.
Compound 4j: 1H NMR (300 MHz, CDCl3): δ = 7.34 (d, J = 11.4 Hz, 1 H), 6.55 (dd, J = 14.7, 10.5 Hz, 1 H), 6.39 (dd, J = 14.7, 11.4 Hz, 1 H), 6.22 (dd, J = 14.1, 10.5 Hz, 1 H), 5.96 (dq, J = 14.1, 6.8 Hz, 1 H), 1.95 (s, 3 H), 1.85 (d, J = 6.8 Hz, 3 H). 13C NMR (75 MHz, CDCl3): δ = 173.7 (s), 141.0 (2 d), 135.0 (d), 131.6 (d), 125.2 (d), 125.0 (s), 18.6 (q), 12.3 (q). IR: (KBr): ca. 3000, 1678, 1601, 1427, 1316, 1268, 987, 929 cm-1. MS (EI): m/z = 152 [M]+, 107 [M - CO2H]+.
Compound 4k: 1H NMR (400 MHz, CDCl3): δ = 6.47 (s, 1 H), 5.92 (s, 1 H), 5.75 (s, 1 H), 3.19 (s, 2 H), 2.24 (s, 2 H), 2.22 (s, 2 H), 1.05 (s, 6 H). 13C NMR (100 MHz, CDCl3): δ = 28.3 (2 q), 33.7 (s), 39.6 (t), 43.8 (t), 51.0 (t), 125.8 (d), 130.3 (t), 136.0 (s), 161.1 (s), 171.1 (s), 200.6 (s). IR: (KBr): ca. 3000, 2929, 1720, 1667, 1372, 1160, 982 cm-1. MS (EI): m/z = 208 [M]+, 163 [M - CO2H]+.