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Synlett 2002(5): 0751-0754
DOI: 10.1055/s-2002-25357
LETTER
© Georg Thieme Verlag Stuttgart · New York

Multi-functionalized 2,2′:6′,2′′-Terpyridines

Marcel Hellera,b, Ulrich S. Schubert*b,c
a Lehrstuhl für Makromolekulare Stoffe, Technische Universität München, Lichtenbergstr. 4, 85747 Garching, Germany
b Center for NanoScience, LMU München, Amalienstr. 54, 80799 München, Germany
c Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
Fax: +31(40)2474186; e-Mail: u.s.schubert@tue.nl.;
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Publication History

Received 13 February 2002
Publication Date:
07 February 2007 (online)

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Abstract

In this contribution, Stille-type cross-coupling procedure is shown to be an easy and universal way to prepare a variety of functionalized terpyridines. They may be functionalized in one step with different substituents at the outer pyridine rings and at the 4′-position of the centered ring, leading to multi-functionalized compounds. The initially obtained methylester and ethylester groups may be simply converted into bromomethyl and hydroxymethyl groups, which allow further functionalization reactions.

Key words

terpyridine synthesis - Stille cross-coupling - functional groups - multidentate ligands - multifunctionality

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Dimethyl-2,2′:6′,2′′-terpyridines. Route 1: The methyl-2-tributylstannylpyridine 2a-c (3 g, 7.85 mmol), 2,6-dibromopyridine 1 (0.75 g, 3.17 mmol) and tetrakis-(triphenylphosphine)-palladium(0) (0.29 g, 6.0 mol%) are refluxed for 4 days in absolute toluene (50 mL). After removal of the solvent, the black residue is treated with aq HCl (6 M). The suspension is extracted with CH2Cl2 and the organic phase is washed again with HCl (6 M). The aq solution is added dropwise into cold aq ammonia (10%). The precipitate is filtered off, dissolved in CH2Cl2, dried over Na2SO4, the solvent is removed again and the residue is crystallized from ethyl acetate. Route 2: 2,6-Bis(trimethyl-stannyl)pyridine 6 (12.23 g, 7.66 mmol), the 2-bromo-methylpyridine 7a-c (3.29 g, 19.15 mmol) and tetrakis-(triphenylphosphine)-palladium(0) (0.6 g, 6 mol%) are refluxed in dry toluene (70 mL) for 72 h at 110 °C. The workup is identical to route 1. 3: White crystals. Mp 186 °C. 1H NMR (CDCl3): δ = 2.39 (s, 6 H, CH 3 ), 7.17 (dd, J = 4.96 Hz, 0.77 Hz, 2 H, H5,5 ′′ ), 7.94 (t, J = 8.01 Hz, 1 H, H4 ′), 8.41 (s, 2 H, H3,3 ′′), 8.42 (d, J = 8.01 Hz, 2 H, H3 ′ ,5 ′), 8.56 (d, J = 4.95 Hz, 2 H, H6,6 ′′). C17H15N3 (261.32): Calcd C, 78.13; H, 5.79; N, 16.08. Found: C, 78.04; H, 6.00; N, 15.92. 4: White crystals (Lit. [15] 67%). Mp 173 °C (Lit. [15] 169-171 °C, Lit. [15] 174-175 °C). 1H NMR (CDCl3): δ = 2.39 (s, 6 H, CH 3), 7.63 (dd, J = 8.01, 2.28 Hz, 2 H, H4,4 ′′), 7.91 (t, J = 7.82 Hz, 1 H, H4 ′), 8.38 (d, J = 7.62 Hz, 2 H, H3 ′ ,5 ′), 8.49 (d, J = 8.40 Hz, 2 H, H3,3 ′′), 8.50 (s, 2 H, H6,6 ′′). C17H15N3 (261.32): Calcd C, 78.13; H, 5.79; N, 16.08. Found: C, 77.92; H, 5.73; N, 16.07. 5: White crystals. Mp 171 °C (Lit. [16] >250 °C). 1H NMR (CDCl3): δ = 2.65 (s, 6 H, CH 3 ), 7.18 (d, J = 7.63 Hz, 2 H, H5,5 ′′), 7.73 (t, J = 7.63 Hz, 2 H, H4,4 ′′), 7.93 (t, J = 8.01 Hz, 1 H, H4 ′), 8.41 (d, J = 7.63 Hz, 2 H, H6,6 ′′), 8.47 (d, J = 8.01 Hz, 2 H, H3 ′ ,5 ′). C17H15N3 (261.32): Calcd C, 78.13; H, 5.79; N, 16.08. Found: C, 78.42; H, 5.63; N, 16.16.

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5′,5′′-Bis(bromomethyl)-2,2′:6′,2′′-terpyridine-4′-ethylester 17 (0.5 g, 1.0 mmol) is dissolved in pure acetic acid (20 mL) and dry sodium acetate (82 mg, 1.0 mmol) is added. The mixture is heated under reflux for 1 h. After cooling, the solution is added dropwise to cold aq ammonia (10%). The oily product is extracted with CH2Cl2, washed with brine, dried and crystallized from ethyl acetate after removal of the solvent. Yield 0.31 g (71%). Mp 231 °C. 1H NMR (CDCl3): δ = 1.42 (t, J = 6.06 Hz, 3 H, OCH2CH 3), 2.10 (s, 6 H, OCOCH 3), 4.45 (q, J = 7.06 Hz, 2 H, OCH 2CH3), 5.17 (s, 4 H, Ar-CH 2 O), 7.83 (dd, J = 8.01, 2.20 Hz, 2 H, H4,4 ′′), 8.50 (d, J = 8.02 Hz, 2 H, H3,3 ′′), 8.57 (s, 2 H, H6,6 ′′), 8.90 (s, 2 H, H3 ′ ,5 ′). C24H23N3O6 (449.46): Calcd C, 64.13; H, 5.16; N, 9.35. Found: C, 64.55; H, 4.80; N, 9.01.