Synlett 2008(7): 1050-1052  
DOI: 10.1055/s-2008-1072675
LETTER
© Georg Thieme Verlag Stuttgart · New York

Regioselective Synthesis of Functionalized Resorcins by Cyclization of 1,3-Bis(trimethylsilyloxy)-1,3-butadienes with 3,3-Dimethoxypentanoyl Chloride

Muhammad Shera,b, Peter Langer*a,b
a Institut für Chemie, Universität Rostock, Albert Einstein Str. 3a, 18059 Rostock, Germany
e-Mail: peter.langer@uni-rostock.de;
b Leibniz-Institut für Katalyse e. V. an der Universität Rostock, Albert Einstein Str. 29a, 18059 Rostock, Germany
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Publikationsverlauf

Received 3 December 2007
Publikationsdatum:
28. März 2008 (online)

Abstract

Functionalized resorcins are regioselectively prepared by cyclization of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 3,3-dimethoxypentanoyl chloride. The regioselectivity is controlled by the type of Lewis acid employed.

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Typical Procedure for the Synthesis of 6a-l
To a CH2Cl2 solution (8 mL) of 1,3-bis(trimethylsilyloxy)-1-methoxy-1,3-butadiene (5a, 860 mg, 3.32 mmol) and of 4 (660 mg, 3.65 mmol) was dropwise added TMSOTf (0.3 mL, 1.66 mmol, 0.5 equiv) at -78 °C. The reaction mixture was allowed to warm to 20 °C during 6-12 h. After stirring for additional 2-6 h at 20 °C, HCl (10%, 25 mL) was added. The organic and the aqueous layers were separated and the latter was extracted with CH2Cl2 (3 × 20 mL). The combined organic layers were dried (NaSO4), filtered, and the filtrate was concentrated in vacuo. The residue was purified by chromatography (SiO2, heptanes-EtOAc) to give 6a as yellow solid (280 mg, 43%). 1H NMR (300 MHz, CDCl3): δ = 1.13 (t, 3 H, J = 7.6 Hz, CH3), 2.48 (q, 2 H, J = 7.5 Hz, CH2), 3.99 (s, 3 H, OCH3), 6.28 (s, 2 H, CHAr), 9.54 (s, 2 H, OH). 13C NMR (75 MHz, CDCl3): δ = 14.4 (CH3), 29.2 (CH2), 52.7 (OCH3), 97.7 (C), 107.8 (CH), 154.6,164.5, 169.8 (C). IR (KBr): 3427 (s), 2960 (s), 1670 (s), 1571 (s), 1377 (m), 1257 (s), 1103 (s), 1040 (m), 949 (m), 846 (s)799 (s), 738 (s), 613 (s), 531 (m) cm-1. GC-MS (EI, 70 eV): m/z (%) = 196.0(35) [M+], 164.0(100), 136.0(21), 121.0(27). Anal. Calcd for C10H12O4 (196.07): C, 61.22; H, 6.16. Found: C, 61.32; H, 6.11.

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Typical Procedure for the Synthesis of 7a-i To a CH2Cl2 solution (5 mL) of 1,3-bis(trimethylsilyloxy)-1-methoxy-1,3-butadiene (500 mg, 1.91 mmol) and of 4 (385 mg, 2.11 mmol) was added dropwise TiCl4 (0.21 mL, 1.91 mmol) at -78 °C. The reaction mixture was allowed to warm to 20 °C during 6-12 h. After stirring for additional 2-6 h at 20 °C, a sat. aq solution of NaHCO3 (20 mL) was added. The organic and the aqueous layers were separated and the latter was extracted with Et2O (3 × 25 mL). The combined organic layers were dried (NaSO4), filtered and the filtrate was concentrated in vacuo. The residue was purified by chromatography (SiO2, heptane-EtOAc) to give 7a as a yellow solid (230 mg, 61%). 1H NMR (300 MHz, CDCl3): δ = 1.30 (t, 3 H, J = 7.5 Hz, CH3), 3.28 (q, 2 H, J = 7.5 Hz, CH2), 4.01 (s, 3 H, OCH3), 6.08 (s, 1 H, CHAr), 6.78 (s, 1 H, CHAr), 12.06 (s, 1 H, OH). 13C NMR (75 MHz, CDCl3): δ = 14.8 (CH3), 28.8 (CH2), 52.7 (OCH3), 110.5, 116.0, 155.0, 166.0, 167.6, 170.5, 179.9. IR (KBr): 3427 (s), 2960 (s), 1670 (s), 1571 (s), 1377 (m), 1257 (s), 1103 (s), 1040 (m), 949 (m), 846 (s), 799 (s), 738 (s), 613 (s), 531 (m)
cm-1. GC-MS (EI, 70 eV): m/z (%) = 196.0(37) [M+], 164.0(100), 136.0(26), 121.0(27). HRMS (EI): m/z calcd for C10H12O4 [M]+: 196.072572; found: 196.07301.