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Synlett 2008(7): 963-966  
DOI: 10.1055/s-2008-1072654
LETTER
© Georg Thieme Verlag Stuttgart · New York

Synthesis of Functionalized Biaryls Based on a Heck Cross-Coupling-[3+3] Cyclization Strategy

Gerson Mroßa, Helmut Reinkea, 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
Further Information

Publication History

Received 15 January 2008
Publication Date:
28 March 2008 (online)

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Abstract

6-Arylsalicylates were regioselectively prepared by formal [3+3] cyclization of 1,3-bis(silyloxy)-1,3-butadienes with 1-aryl-3-ethoxyprop-2-en-1-ones which are available by Heck reaction of benzoyl chlorides with ethylvinyl ether. In this context, the first [3+3] cyclizations of brominated substrates are reported.

Key words

arenes - cyclizations - regioselectivity - silyl enol ethers

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Typical Procedure for the Heck Reaction of Ethylvinyl Ether with Acid Chlorides
To a mixture of ethylvinyl ether (2.90 g, 40.0 mmol) and of Et3N (1.20 g, 12.0 mmol) in a pressure tube was added Pd(OAc)2 (20 mg, 0.1 mmol) under Ar atmosphere. The mixture was stirred until a clear yellow solution was formed. To the mixture were added benzoylchloride (1.20 g, 10.0 mmol), and the mixture was stirred at 80 °C for 24 h. The mixture was poured into Et2O (50 mL) and the solid (triethylammonium hydochloride) was filtered off. The filtrate was concentrated under reduced pressure and the residue was purified by chromatography (SiO2, heptanes-EtOAc = 10:1 → 5:1) to give 3a as a slightly yellow oil (3.80 g, 55%).

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General Procedure for the Synthesis of Salicylates 5 To a CH2Cl2 solution (1 mL) of 3a (176 mg, 1.0 mmol) and 4a (260 mg, 1.0 mmol) was added a CH2Cl2 solution (1 mL) of TiCl4 (0.12 mL, 1.0 mmol) at -78 °C. The temperature of the solution was allowed to warm to 20 °C within 14 h. To the mixture was added CH2Cl2 (10 mL) and HCl (10 mL, 10%). The organic and the aqueous layer were separated and the latter was extracted with CH2Cl2. The combined organic layers were dried (Na2SO4), filtered, and the filtrate was concentrated in vacuo. The residue was purified by chromatography (heptane-EtOAc, 10:1) to give 5a as a slightly yellow oil (0.081 g, 36%).
Methyl 6-phenylsalicylate (5a): 1H NMR (300 MHz, CDCl3): δ = 3.47 (s, 3 H, OCH3), 6.80 (d, 3 J = 7.4 Hz, 1 H, CH), 6.99 (d, 3 J = 7.4 Hz, 1 H, CH), 7.20-7.43 (m, 6 H, CH), 10.60 (s, 1 H, OH). 13C NMR (50.3 MHz, CDCl3): δ = 52.1 (OCH3), 112.5 (CHPh/Ar), 117.0, 123.0, 127.3, 128.0, 128.5, 134.1, 143.1, 145.3, 161.7, 171.8 (CO). IR (neat) = 3060 (m), 2952 (m), 1667 (s), 1601 (s), 1572 (m), 1501 (w), 1439 (s), 1343 (m), 1271 (s), 1220 (s) cm-1. MS (EI, 70 eV): m/z (%) = 228 (36) [M+], 196 (100), 168 (53), 139 (34). ESI-HRMS: m/z calcd for C14H12O3 [M + 1]+: 228.07864; found: 228.07866.

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CCDC-679813 and CCDC-679814 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.