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Synlett 2008(12): 1889-1893  
DOI: 10.1055/s-2008-1078507
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Ultrasound-Assisted Synthesis of Functionalized 1,3-Enynes by Palladium-Catalyzed Cross-Coupling Reaction of α-Styrylbutyltelluride with Alkynyltrifluoroborate Salts

Fateh Veer Singha, Minéia Weberb, Rafael Carlos Guadagnina, Hélio A. Stefani*a,b
a Departamento de Farmácia, Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, São Paulo, SP, Brazil
Fax: +55(11)8154418; e-Mail: hstefani@usp.br;
b Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, SP, Brazil
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Publication History

Received 17 March 2008
Publication Date:
19 June 2008 (online)

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Abstract

An ultrasound-assisted synthesis of functionalized 1,3-enyne scaffolds is described and illustrated by palladium-catalyzed cross-coupling of potassium alkynyltrifluoroborate salts and α-styrylbutyltellurides. This procedure offers easy access to 1,3-enyne architecture that contains aliphatic and aromatic groups in good to excellent yields.

Key words

cross-coupling reaction - 1,3-enyne - α-styrylbutyltelluride - potassium alkynyltrifluroborate salts

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General Procedure for the Synthesis of 3a-h
A suspension of α-styrylbutyltelluride (1, 0.143 g, 0.5 mmol), potassium alkynyltrifluoroborate salt(2) (0.103 g, 0.50 mmol), Pd(PPh3)4 (0.055 g, 0.05 mmol), Et3N (0.101g, 1 mmol) and AgOAc (0.083 g, 0.5 mmol) in MeOH (3 mL) was irradiated in a water bath of an ultrasonic cleaner for 20 min. Then, the reaction was diluted with EtOAc (30 mL). The organic layer was washed with sat. solution of NH4Cl (2 × 10 mL) and H2O (2 × 10 mL), dried over MgSO4, and concentrated under vacuum. The crude product was purified by flash column chromatography (SiO2) using hexane as eluent and characterized as follows:
But-3-en-1-yne-1,3-diyldibenzene (3a): yellow oil. ¹H NMR (300 MHz, CDCl3): δ = 5.80 (s, 1 H, CH), 6.03 (s, 1 H, CH), 7.32-7.48 (m, 5 H, ArH), 7.54-7.61 (m, 3 H, ArH), 7.74-7.81 (m, 2 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 88.56, 90.78, 120.67, 123.11, 126.12, 128.36, 128.42, 129.21, 130.63, 131.68, 132.51, 137.28. IR (neat): 755.84, 782.57, 1111.48, 1225.69 cm-¹. GC-MS: m/z (relative intensity, %) = 204 (100), 203 (81), 202 (92), 101 (45).
2-Methoxy-6-(3-phenylbut-3-em-1ynyl)naphthalene (3b): colorless oil. ¹H NMR (300 MHz, CDCl3): δ = 3.94 (s, 3 H, OMe), 5.80 (s, 1 H, CH), 6.00 (s, 1 H, CH), 7.11-7.20 (m, 2 H, ArH), 7.27 (s, 1 H, ArH), 7.33-7.46 (m, 3 H, ArH), 7.55 (d, J = 8.6 Hz, 1 H, ArH), 7.68-7.81 (m, 3 H, ArH), 7.99 (s, 1 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 55.38, 88.26, 91.42, 105.83, 117.99, 119.48, 120.49, 126.87, 128.10, 128.37, 128.45, 128.50, 129.04, 129.38, 130.76, 131.42, 134.23, 137.40. IR (neat): 747.75, 776.73, 1123.46, 1232.64 cm-¹. GC-MS: m/z (relative intensity, %) = 284 (100), 269 (10), 241 (45), 120 (45).
tert-Butyldimethyl(4-phenylpent-4-en-2-ynyloxy)silane (3c): colorless oil. ¹H NMR (300 MHz, CDCl3): δ = 0.17 (s, 6 H, 2 Me), 0.93 (s, 9 H, 3 Me), 4.55 (s, 2 H, CH2), 5.66 (s, 1 H, CH), 5.92 (s, 1 H, CH), 7.27-7.39 (m, 3 H, ArH), 7.63-7.69 (m, 2 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = -5.08, 18.32, 25.82, 52.20, 83.92, 89.35, 120.70, 125.57, 126.03, 128.30, 130.27, 137.09. IR (neat): 761.12, 789.67, 1104.28, 1218.70 cm-¹. GC-MS: m/z (relative intensity, %) = 272 (100), 257 (18), 242 (28), 167 (48).
Dec-1-en-3-yn-2-ylbenzene (3d): colorless oil. ¹H NMR (300 MHz, CDCl3): δ = 0.90 (t, J = 6.6 Hz, 3 H, Me), 1.28-1.67 (m, 8 H, 4 CH2), 2.40 (t, J = 6.6 Hz, 2 H, CH2), 5.57 (s, 1 H, CH), 5.83 (s, 1 H, CH), 7.27-7.51 (m, 3 H, ArH), 7.62-7.69 (m, 2 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 14.05, 19.42, 22.58, 28.65, 28.72, 31.36, 79.76, 92.10, 119.30, 126.07, 128.08, 128.25, 131.00, 137.83. IR (neat): 750.00, 773.47, 1134.53, 1227.52 cm-¹. GC-MS: m/z (relative intensity, %) = 212 (43), 197 (40), 183 (32), 169 (52), 155 (82), 141 (100), 129 (67).
[4-(1-Methoxycyclohexyl)but-1-en-3-yn-2-yl]benzene (3e): colorless oil. ¹H NMR (300 MHz, CDCl3): δ = 1.23-1.36 (m, 2 H, CH2), 1.59-1.70 (m, 6 H, 3 CH2), 1.96-2.04 (m, 2 H, CH2), 3.53 (s, 3 H, OMe), 5.66 (s, 1 H, CH), 5.91 (s, 1 H, CH), 7.23-7.40 (m, 3 H, ArH), 7.62-7.68 (m, 2 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 22.92, 25.50, 36.83, 50.91, 74.41, 85.22, 91.91, 120.58, 126.00, 128.28, 128.38, 130.29, 137.33. IR (neat): 745.94, 769.78, 1127.56, 1240.67 cm-¹. GC-MS: m/z (relative intensity, %) = 240 (19), 225 (51), 197 (100), 137 (100).
(4-Cyclohexenylbut-1-em-3yn-2yl)benzene (3f): colorless oil. ¹H NMR (300 MHz, CDCl3): δ = 1.61-1.69 (m, 4 H, 2 CH2), 2.11-2.24 (m, 4 H, 2 CH2), 5.61 (s, 1 H, CH), 5.87 (s, 1 H, CH), 6.21 (s, 1 H, CH), 7.29-7.36 (m, 3 H, ArH), 7.62-7.68 (m, 2 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 21.30, 22.11, 25.55, 29.00, 85.78, 92.60, 119.41, 120.46, 125.85, 127.97, 128.08, 130.62, 135.22, 137.34. IR (neat): 754.41, 780.07, 1121.48 cm-¹. GC-MS: m/z (relative intensity, %) = 208 (100), 178 (64), 165 (55), 115 (26).
(5-Methoxy-5-methylhept-1-em-3-yn-2yl)benzene (3g): colorless oil. ¹H NMR (300 MHz, CDCl3): δ = 1.03 (t, J = 7.4 Hz, 3 H, Me), 1.46 (s, 3 H, Me), 1.69-1.88 (m, 2 H, CH2), 3.40 (s, 3 H, OMe), 5.64 (s, 1 H, CH), 5.90 (s, 1 H, CH), 7.22-7.50 (m, 3 H, ArH), 7.59-7.66 (m, 2 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 8.52, 24.87, 33.81, 51.38, 74.32, 84.25, 91.64, 120.39, 125.74, 128.05, 128.13, 129.99, 137.06. IR (neat): 759.83, 788.50, 1105.48, 1236.67 cm-¹. GC-MS: m/z (relative intensity, %) = 214 (4), 199 (8), 185 (100).
Hexa-1,5-dien-3yne-2,5-diyldibenzene (3h): colorless oil. ¹H NMR (300 MHz, CDCl3): δ = 5.76 (s, 2 H, 2 CH), 5.98 (s, 2 H, 2 CH), 7.22-7.50 (m, 6 H, ArH), 7.59-7.66 (m, 4 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 89.70, 120.84, 125.89, 128.15, 128.22, 130.36, 137.00. IR (neat): 743.60, 778.43, 1134.56, 1234.54 cm-¹. GC-MS: m/z (relative intensity, %) = 230 (100), 215 (40), 202 (17), 115 (49).