Synlett 2009(7): 1063-1066  
DOI: 10.1055/s-0028-1088208
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

The Sonogashira Cross-Coupling Reaction of Alkenyl Chlorides with Aliphatic Acetylenes

Matija Gredičak, Ivanka Jerić*
Division of Organic Chemistry and Biochemistry, Ruer Bošković Institute, 10002 Zagreb, Croatia
Fax: +385(1)4680195; e-Mail: ijeric@irb.hr;
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Publikationsverlauf

Received 22 January 2009
Publikationsdatum:
16. März 2009 (online)

Abstract

The Sonogashira cross-coupling reaction between amino acid based alkenyl chlorides and aliphatic acetylenes is reported. The present approach can be used in natural product synthesis and as an alternative to usually more expensive and unstable vinyl-­iodides.

11

Boc-(prop-2-yne-1-yl)-Gly-OH (5) was prepared according to the procedure described in ref. 8. Yield 74%; yellow oil; R f  = 0.44 (toluene-EtOAc-AcOH, 10:2:0.5). ¹H NMR (300 MHz, CDCl3, trans and cis): δ = 1.45, 1.49 (s, 9 H, CH3 Boc), 2.28 (br t, 1 H, H3 propargyl), 4.17 (m, 4 H, H11′ propargyl, α Gly). ¹³C NMR (75 MHz, CDCl3, trans and cis): δ = 28.2 (CH3 Boc), 36.6, 37.3 (C1 propargyl), 47.1 (α Gly), 72.7, 73.0 (C3 propargyl), 78.5 (C Boc), 81.4, 81.6 (C2 propargyl), 154.6, 154.8 (CO Boc), 175.3 (CO Gly). HRMS (MALDI): m/z [M + Na]+ calcd for C10H15NNaO4: 236.0893; found: 236.0887.

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Synthesis of Boc-[penta-5-chloro-4-( Z )-ene-2-yne-1-yl]-Gly-OH (6)
A mixture of Pd(Ph3P)4 (12 mg, 0.035 mmol), CuI (12 mg, 0.053 mmol), cis-DCE (65 µL, 0.7 mmol), and piperidine (136 µL, 1.40 mmol) dissolved in dry THF (1 mL) was stirred for 30 min under argon. A solution of Boc-(prop-2-yne-1-yl)-Gly-OH (5, 75 mg, 0.35 mmol) and piperidine (68 µL, 0.70 mmol) in THF (2 mL) was added dropwise by the syringe, and the reaction was stirred at r.t. overnight. Solvent was evaporated, and the residue purified by flash chroma-tography. Yield 59% (56 mg); yellow oil; R f  = 0.54 (toluene-EtOAc-AcOH, 10:2:0.5). ¹H NMR (300 MHz, DMSO-d 6, trans and cis): δ = 1.36, 1.41 (s, 9 H, CH3 Boc), 2.69 (s, 1 H, H3 chloroenyne), 3.91, 3.93 (br s, 2 H, α Gly), 4.26, 4.28 (H11′ chloroenyne), 6.19 (br td, 1 H, H4 chloro-enyne), 6.79 (d, ³ J 4,5 = 7.3 Hz, 1 H, H5 chloroenyne). ¹³C NMR (75 MHz, DMSO-d 6, trans and cis): δ = 27.8, 27.9 (CH3 Boc), 37.3, 38.03 (C1 chloroenyne), 47.4, 47.7 (α Gly), 77.6, 77.9 (C Boc), 79.9, 80.0 (C2 chloroenyne), 93.4, 93.5 (C3 chloroenyne), 112.0 (C4 chloroenyne), 129.1 (C5 chloroenyne), 154.6, 154.2 (CO Boc), 170.7 (CO Gly). HRMS (MALDI): m/z [M + Na]+ calcd for C12H16ClNNaO4: 296.0660; found: 296.0652.

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Synthesis of Boc-[octa-8-hydroxy-2,6-diyne-4-( Z )-ene-1-yl]-Gly-OH (7)
A mixture of Pd(Ph3P)4 (13 mg, 0.011mmol), CuI (10 mg, 0.041 mmol), Boc-[penta-5-chloro-4-(Z)-ene-2-yne-1-yl]-Gly-OH (6, 45 mg, 0.164 mmol), and piperidine (38 µL, 0.41 mmol) dissolved in dry THF (1 mL) was stirred for 30 min under argon. A solution of propargyl alcohol (20 µL, 0.328 mmol) in THF (1 mL) was added dropwise by the syringe, and the reaction was stirred at r.t. overnight. Solvent was evaporated and the residue purified by flash chromatog-raphy. Yield 67% (32 mg); yellow oil; R f  = 0.60 (EtOAc-toluene-AcOH, 10:5:0.5). ¹H NMR (300 MHz, DMSO-d 6): δ = 1.37 (s, 9 H, CH3 Boc), 3.94 (br s, 2 H, α Gly), 4.27 (br d, 4 H, H11′, H88′ enediyne), 6.00 (br td, 1 H, H4 enediyne), 6.04 (br td, 1 H, H5 enediyne). ¹³C NMR (75 MHz, DMSO-d 6): δ = 27.8 (CH3 Boc), 37.2 (C1 enediyne), 47.4 (α Gly), 49.4 (C8 enediyne), 79.5 (C Boc), 79.8 (C2 enediyne), 81.3 (C7 enediyne), 92.4 (C3 enediyne), 97.5 (C6 enediyne), 119.0 (C4 enediyne), 120.1 (C5 enediyne), 154.2 (CO Boc), 170.8 (CO Gly). HRMS (MALDI): m/z [M + H]+ calcd for C15H19NO5: 294.1336; found: 294.1322.

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General Procedure for the Synthesis of 8 (PhCN)2PdCl2, (0.02 mmol), CuI (0.02 mmol), 2 (0.2 mmol), and piperidine (0.40 mmol) were dissolved in dry THF (1 mL), and the reaction was stirred for 30 min under argon. A solution of 5 (0.40 mmol) and piperidine (0.80 mmol) in 2 mL of dry THF was added dropwise by the syringe, and the reaction was stirred at r.t. until all acetylene was consumed. Solvent was evaporated and the residue purified by flash column chromatography.
Boc 2 -Tyr- N -[octa-2,6-diyne-4-( Z )-ene-1,8-diyl](Boc)-Gly-OH (8a) Yield 51%; yellow oil; R f  = 0.64 (toluene-EtOAc-AcOH, 5:5:0.5); t R = 11.54 min. ¹H NMR (300 MHz, CD3OD): δ = 1.37, 1.44, 1.48, 1.52 (s, 27 H, CH3 Boc), 2.87, 3.08 (dd, ³ J α , β = 8.4 Hz, ³ J α , β  = 5.9 Hz, ² J β , β  = 13.5 Hz, 2 H, ββ′ Tyr), 4.12 (m, 5 H, α Tyr, α Gly, H88′ enediyne), 7.04 (d, ³ J δ , ε = 8.4 Hz, 2 H, ε Tyr), 4.35 (br d, 2 H, H11′ enediyne), 5.89 (s, 2 H, H4,5 enediyne), 7.26 (d, ³ J δ , ε = 8.4 Hz, 2 H, δ Tyr). ¹³C NMR (75 MHz, CD3OD, trans and cis): δ = 28.0, 28.6, 28.7, 28.8 (CH3 NHBoc, OBoc), 30.5 (C1 enediyne), 38.6 (β Tyr), 38.9, 39.3 (C8 enediyne), 48.1 (α Gly), 57.4 (α Tyr), 80.9, 81.0, 84.4 (C Boc), 82.4, 82.5, 82.9, 83.00 (C2, C7 enediyne), 92.6, 92.7, 93.8, 93.9 (C3, C6 enediyne), 120.4, 120.5 (C4 enediyne), 120.9, 121.1 (C5 enediyne), 122.3 (ε Tyr), 131.6 (δ Tyr), 136.2 (γ Tyr), 151.6, 153.6 (CO Boc), 156.8, 157.7 (ζ Tyr), 173.2, 173.3 (CO Gly), 173.9 (CO Tyr). HRMS (MALDI): m/z [M + Na]+ calcd for C34H45N3NaO10: 678.2997; found: 678.2980.
Boc-Phe- N -[octa-2,6-diyne-4-( Z )-ene-1,8-diyl](Boc)-Gly-OH (8b)
Yield 58%; yellow oil; R f  = 60 (toluene-EtOAc-AcOH, 5:5:0.5); t R = 10.59 min. ¹H NMR (300 MHz, CD3OD): δ = 1.36, 1.44, 1.47 (s, 18 H, CH3 Boc), 2.85, 3.08 (dd, ³ J α , β = 8.7 Hz, ³ J α , β  = 5.7 Hz, ² J β , β  = 13.5 Hz, 2 H, ββ Phe), 4.10 (m, 4 H, H88′ enediyne, α Gly), 4.27 (m, 1 H, α Phe), 4.35 (br d, 2 H, H11′ enediyne), 5.88 (s, 2 H, H4,5 enediyne), 7.22 (m, 5 H, arom. Phe). ¹³C NMR (75 MHz, CD3OD, trans and cis): δ = 28.6, 28.7, 28.8 (CH3 Boc), 30.5 (C1 enediyne), 38.6, 39.2 (C8 enediyne), 39.5 (β Phe), 48.2 (α Gly), 57.4 (α Phe), 80.8, 81.0 (C Boc), 82.4, 82.5, 82.9, 83.0 (C2, C7 enediyne), 92.6, 92.7, 93.8, 93.9 (C3, C6 enediyne), 120.3, 120.4 (C4 enediyne), 120.9, 121.0 (C5 enediyne), 127.8 (ζ Phe), 129.5 (ε Phe), 130.6 (δ Phe), 138.5 (γ Phe), 156.8, 157.6 (CO Boc), 173.2 (CO Gly), 174.1 (CO Phe). HRMS (MALDI): m/z [M + Na]+ calcd for C29H37N3NaO7: 562.2523; found: 562.2509.
Boc-Val- N -[octa-2,6-diyne-4-( Z )-ene-1,8-diyl](Boc)-Gly-OH (8c) Yield 64%; yellow oil; R f  = 0.57 (toluene-EtOAc-AcOH, 5:5:0.5); t R = 10.22 min. ¹H NMR (300 MHz, CD3OD): δ = 0.94 (br t, 6H, γ Val), 1.44 (br s, 18 H, CH3 Boc), 2.01 (s, 1 H, β Val), 3.85 (d, ³ J α , β = 6.9 Hz, 1 H, α Val), 4.14 (m, 4 H, H88′ enediyne, α Gly), 4.36 (br d, 2 H, H11′ enediyne), 5. 87 (s, 2 H, H4,5 enediyne). ¹³C NMR (75 MHz, CD3OD, trans and cis): δ = 18.7, 19.8 (γ Val), 28.6, 28.7, 28.8 (CH3 Boc), 30.4 (C1 enediyne), 32.4 (β Val), 38.6, 39.2 (C8 enediyne), 48.1 (α Gly), 61.6 (α Val), 80.7, 80.9 (C, Boc), 82.4, 82.5, 82.8, 83.0, (C2, C6 enediyne), 92.5, 92.6, 93.9, 94.0 (C3, C7 enediyne), 120.3, 120.4 (C4 enediyne), 120.8, 120.9 (C5 enediyne), 156.8 (CO Boc), 173.3 (CO Gly), 174.4 (CO Val). HRMS (MALDI): m/z [M + Na]+ calcd for C25H37N3NaO7: 514.2524; found: 514.2537.


Boc-Gly- N -[octa-2,6-diyne-4-( Z )-ene-1,8-diyl](Boc)-Gly-OH (8d) Yield 37%; yellow oil; R f  = 0.27 (toluene-EtOAc-AcOH, 5:5:0.5); t R = 9.14 min. ¹H NMR (600 MHz, CD3OD): δ = 1.45 (s, 18 H, CH3 Boc), 3.72 (br s, 2 H, α Gly¹), 4.09, 4.12 (br s, 2 H, H88′ enediyne), 4.20 (br s, 2 H, α Gly²), 4.34, 4.36 (br s, 2 H, H11′ enediyne), 5.87 (s, 2 H, H4,5 enediyne). ¹³C NMR (150 MHz, CD3OD, trans and cis): δ = 28.6, 28.7, 28.8 (CH3 Boc), 30.5 (C1 enediyne), 38.6, 39.3 (C8 enediyne), 44.7 (α Gly¹) 48.2 (α Gly²), 80.9 (C Boc), 82.4, 82.5, 82.9 (C2, C7 enediyne), 92.6, 92.7, 94.0 (C3, C6 enediyne), 120.3, 120.4 (C4 enediyne), 120.8, 121.0 (C5 enediyne), 156.8, 157.7 (CO Boc), 172.4 (CO Gly¹), 173.4 (CO Gly²). HRMS (MALDI): m/z [M + Na]+ calcd for C22H31N3NaO7: 472.2054; found: 472.2066.
Boc-Ala- N -[octa-2,6-diyne-4-( Z )-ene-1,8-diyl](Boc)-Gly-OH (8e) Yield 77%; yellow oil; R f  = 0.40 (toluene-EtOAc-AcOH, 5:5:0.5); t R = 9.40 min. ¹H NMR (600 MHz, CD3OD): δ = 1.30 (d, ³ J α , β = 7.2 Hz, 3 H, β Ala), 1.44 (s, 18 H, CH3 Boc), 4.11 (m, 3 H, α Ala, α Gly), 4.18 (br d, 2 H, H88′ enediyne), 4.34 (br d, 2 H, H11′ enediyne), 5.88 (s, 2 H, H4,5 enediyne). ¹³C NMR (150 MHz, CD3OD, trans and cis): δ = 18.5 (δ Ala), 28.6, 28.7, 28.8 (CH3 Boc), 30.6 (C1 enediyne), 38.6, 39.3 (C8 enediyne), 48.1 (α Gly), 51.7 (α Ala), 80.8, 80.9, 81.0 (C Boc), 82.4, 82.5, 83.0 (C2, C7 enediyne), 92.5, 94.0 (C3, C6 enediyne), 120.3, 120.4 (C4 enediyne), 120.9, 121.0 (C5 enediyne), 156.8, 157.7 (CO Boc), 173.3 (CO Gly), 175.7, 175.7 (CO, Ala). HRMS (MALDI): m/z [M + Na]+ calcd for C23H3N3NaO7: 486.2211; found: 486.2233.
Boc-Lys(Boc)- N -[octa-2,6-diyne-4-( Z )-ene-1,8-diyl]- (Boc)-Gly-OH (8f) Yield 69%; yellow oil; R f  = 0.24 (toluene-EtOAc-AcOH, 5:5:0.5); t R = 10.07 min. ¹H NMR (300 MHz, CD3OD): δ = 1.43, 1.44 (br d, 31 H, CH3 Boc, γγ′, δδ′ Lys), 1.75 (m, 2 H, ββ′ Lys), 3.03 (t, ³ J δ , ε = 6.6 Hz, 2 H, εε′ Lys), 3.99 (br d, 1 H, α Lys), 4.15 (m, 4 H, H88′ enediyne, α Gly), 4.35 (br d, 2 H, H11′ enediyne), 5.88 (s, 2 H, H4,5 enediyne). ¹³C NMR (75 MHz, CD3OD, trans and cis): δ = 24.3 (γ Lys), 28.6, 28.7, 28.9, 29.0 (CH3 Boc), 30.6 (C1 enediyne), 30.7
(δ Lys), 33.2 (β Lys), 38.6, 39.3 (C8 enediyne), 41.2 (ε Lys), 48.1 (α Gly), 56.1 (α Lys), 80.0, 80.8, 81.0 (C Boc), 82.4, 82.5, 82.9, 83.0 (C2, C7 enediyne), 92.6, 92.7, 94.0 (C3, C6 enediyne), 120.4, 120.5 (C4 enediyne), 120.9, 121.0 (C5 enediyne), 156.7, 156.8, 158.0, 158.7 (CO Boc), 173.2, 173.3 (CO Gly), 175.1 (CO Lys). HRMS (MALDI): m/z
[M + Na]+ calcd for C31H48N4NaO9: 643.3314; found: 643.3296.