Ruthenium Indenylidene and Vinylidene Complexes bearing Schiff Bases: Potential Catalysts in Enol-Ester Synthesis

Tom Opstal; Francis Verpoort

doi:10.1055/s-2002-31892

LETTER

Ruthenium Indenylidene and Vinylidene Complexes bearing Schiff Bases: Potential Catalysts in Enol-Ester Synthesis

Tom Opstal, Francis Verpoort*
Department of Inorganic and Physical Chemistry, Organometallics and Catalysis Division, Ghent University, Krijgslaan 281 (S3), 9000 Ghent, Belgium
Fax: +32(9)2644983; e-Mail: Francis.Verpoort@rug.ac.be;

Abstract

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Abstract

In an extension of our previous investigations on the ruthenium(II) Schiff-base chemistry, complexes 1, 2, 3a-b and 4a-b were synthesized and tested as catalyst for the nucleophilic addition of carboxylic acids to terminal alkynes. A careful choice of the catalytic system, substrate and carboxylic acid can provide alk-1-en-2-yl esters, alk-1-en-1-yl esters synthesis or enyne dimerization. In this way substituted isopropenol and α-methylenebenzyl formates, (geminal, geminal) dienol diesters were synthesized in one step by direct addition of formic acid or benzoic acid to terminal mono- and di-ynes.

Key words

ruthenium - Schiff base - vinylidene - indenylidene - enol ester synthesis - homogeneous catalysis

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References

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Catalyst 2 (Figure [2] ): dark red solid
(79%) ¹H NMR (299.89 MHz, C₆D_6, 25 °C) δ 8.44 (dd, J = 7 Hz, 1H, H-23), 8.17 (s, 1H, H-7), 7.71 (d, J = 4 Hz, 2H, H-26), 7.46 (d, J = 5 Hz, 1H, H-28), 7.44 (dd, J = 8.7, 2.4 Hz, 1H, H-5), 7.38 (dd, J = 6.5, 2.1 Hz, 2H, H-27), 7.37 (s, 1H, H-16), 7.30 (m, 1H, H-21), 7.25 (m, 1H, H-22), 7.23 (dd, J = 7.0, 2.2 Hz, H-20), 6.97 (s, 2H, H-11, H-11), 6.88 (t, J = 6.5 Hz, 1H, H-4), 6.68 (d, J = 9.3 Hz, 1H, H-2), 2.46 (s, 6H, H-10, H-15), 1.85-1.33 (m, 20H, CH₂ of PCy₃), 1.28 (d, J = 6.7 Hz, 3H), 1.15 (m, 10H). ¹³C NMR (75.41 MHz, C₆D₆, 25 °C) 290.6 (s, J _PC = 7.8 Hz, C-16), 162.2 (s, C-7),158.7 (s, C-1), 150.3 (s, C-8), 142.5 (s, C-24), 140.0 (s, C-19), 139.2 (s, C-18), 138.7 (d, J _CH = 175 Hz, C-17), 136.4 (s, C-25), 133. 0 (s, C-9), 131.2 (d, C-3), 130.2 (s, C-11), 129.7 (d, C-5), 129.3 (d, J _CH = 160 Hz, C-23), 129.1 (d, C-22), 128.4 (d, C-21), 128,0 (d, C-28), 126.2 (d, C-26, C-30), 120.9 (d, C-4), 118.2 (s, C-6), 118.0 (d, J _CH = 155 Hz, C-20), 33.7 (CH), 30.2, 30.1, 28.6, 28.3, 21.9 (CH₂ of PCy₃), 16.80 (q, J _CH = 124.9 Hz, C-10, C-16). ³¹P NMR (121,40 MHz, C₆D₆, 25 °C, ref. to H₃PO₄) δ = 39.60 (s). Anal. Calcd for C₄₈H₅₆BrClNOPRu; C, 63.33, H, 6.20, N, 1.54. Found: C, 63.97, H, 6.31, N, 1.70.
Catalyst 3a: brown solid (81%): ¹H NMR (299.89 MHz, C₆D₆, 25 °C): δ 8.20 (d, J = 5.2 Hz, 1H), 7.38 (d, J = 7.0 Hz, 1H), 7.30 (t, J = 7.2 Hz, 1H), 7.22-7.14, 6.99-6.94, 6.89-6.79 (each m, 5H, Ph), 7.13 (s, 2H), 7.06 (t, J = 7 Hz, 1H), 4.36 (t, J = 4.2 Hz, Ru=C=CHPh), 2.14 (s, 3H), 1.61-1.31 (m, 20H), 1.27 (d, J = 6 Hz, 3H), 1.19 (m, 10H); ¹³C NMR (75.41 Hz, C₆D₆, 25 °C): δ 343.6 (d, J _PC = 11.5 Hz, Ru=C=CHPh), 161.25, 154.32, 138.36, 128.49, 118.21, 108.45 (t, J _PC = 5 Hz, Ru=C=CHPh), 31.5 (vt, J = 8.5 Hz, C¹ of C₆H₁₁), 26.16 (s, C^3,5 of C₆H₁₁), 16.76; ³¹P{¹H} NMR (C₆D₆, 25 °C): δ 51.8 Hz (s). Anal. Calcd for C₄₁H₅₂BrClNOPRu; C, 59.89, H, 6.37, N, 1.70. Found: C, 59.93, H, 6.42, N, 1.79.
Catalyst 3b: dark brown solid (80%): ¹H NMR (299.89 MHz, C₆D₆, 25 °C): δ 8.24 (d, J = 2.5 Hz, 1H), 8.08 (dd, J = 9 Hz, 2.4 Hz, 1H), 7.94 (d, J = 5.6 Hz, 1H), 7.56 (t, J = 7.5 Hz, 1H), 7.29 (d, J = 9.8 Hz, 1H), 7.16 (s, 2H), 7.13-7.07 (o-H), 7.02-6.96 (p-H), 6.89-6.80 (m-H) (each m, 5H, Ph), 4.25 (t, J = 5 Hz, Ru=C=CHPh), 2.44 (q, J = 11 Hz, 3H), 2.34 (s, 3H), 1.70-1.63 (br s, 20H, C₆H₁₁), 1.54 (d, J = 12 Hz, 3H), 1.36-1.08 (br s, 20H); ¹³C NMR (75.41 Hz, C₆D₆, 25 °C): δ 340.3 (d, J _PC = 10 Hz, Ru=C=CHPh), 165.3, 162.8, 141.9, 137.7, 132.9 (s, C¹ of Ph), 128.2, 125.5, 121.6 (each s, C^2,6 of C₆H₁₁), 117.7, 111.8, 108.3 (t, J _PC = 5 Hz, Ru = C = C); ³¹P{¹H} NMR (C₆D₆, 25 °C): δ 49.07 Hz (s). Anal. Calcd for C₄₁H₅₁BrClN₂O₃PRu; C, 56.78, H, 5.93, N, 3.23. Found: C, 56.81, H, 6.32, N, 3.30.
Catalyst 4a: dark brown solid(78%): ¹H NMR (299.89 MHz, C₆D₆, 25 °C): δ 8.28 (d, J = 2.7Hz, 1H), 7.42 (d, J = 7.2 Hz, 1H), 7.23 (t, J = 7.0 Hz, 1H),7.06 (m, 3H), 6.74 (d, J = 6.7 Hz, 1H), 2.83 (t, J = 3 Hz, Ru=C=CH t-Bu), 1.78-1.50 (m, 23H), 1.26-1.15 (m, 10H), 1.08 (s, 9H, t-Bu); ¹³C NMR (75.41 Hz, C₆D₆, 25 °C): δ 330.9 (t, J _PC = 13.6 Hz, Ru=C=CHBut^t), 162.2, 158.4, 130.3, 106.0 (t, J_PC = 5.3 Hz, Ru = C = CHBut^t), 35. 1 (vt, J = 9 Hz, C¹ of C₆H₁₁), 26.6
[s, C(CH₃)₃], 21.2 (s, C^3,5 of C₆H₁₁), 19.9 [s, C(CH₃)₃], 16.5; ³¹P{¹H} NMR (C₆D_6, 25 °C): δ 47.443 (s). Anal. Calc for C₃₉H₅₆BrClNOPRu; C, 58.39, H, 7.04, N, 1.75. Found: C, 58.43, H, 7.20, N, 1.89.
Catalyst 4b: brown solid (70%): ¹H NMR (299.89 MHz, C₆D₆, 25 °C): δ 8.30 (d, J = 2.9 Hz, 1H), 7.6 (dd, J = 9, 2.3 Hz, 1H), 7.37 (d, J = 5 Hz, 1H), 7.13 (s, 2H), 6.99 (d, J = 9.8 Hz 1H), 3.06 (t, J = 4 Hz, Ru=C=CH t-Bu), 2.50 (q, J = 12 Hz, 3H), 2.38 (s, 3H), 1.88-1.75 (br s, 20H), 1.60 (d, J = 12.5 Hz, 3H), 1.34-25 (m, 10H), 1.07 (s, 9H, t-Bu); ¹³C NMR (75.41 Hz, C₆D₆, 25 °C): δ 333.20 (t, J _PC = 13.4 Hz, Ru=C=CHt-Bu), 162.02, 157.32, 138.39, 127. 91, 118.16, 111.7 (t, J _PC = 5 Hz, Ru=C=CHt-Bu), 36.20 (vt, J = 8.8 Hz, C¹ of C₆H₁₁), 31.30 (s, C(CH₃)₃, 28.25 (s, C^3,5 of C₆H₁₁), 23.82 [s, C(CH₃)₃], 17.48; ³¹P{¹H} NMR (C₆D_6, 25 °C): δ 45.1 (s). Anal. Calcd for C₃₉H₅₅BrClN₂O₃Pru; C, 55.29, H, 6.54, N, 3.31. Found: C, 55.54, H, 7.13, N, 3.60.

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