A Concise Li/liq. NH₃ Mediated Synthesis of (4E,10Z)-Tetradeca-4,10-dienyl Acetate: The Major Sex Pheromone of Apple Leafminer Moth, Phyllonorycter ringoniella

Experimental

General. All the glassware was dried thoroughly in hot oven and streamed with nitrogen before use. Solvents were dried and purified by conventional methods prior to use. All the chemicals were purchased from Sigma Aldrich (USA). IR measurements of all the samples were performed on FTIR-6300 Spectrometer (JASCO, Japan). 1H NMR (at 400 MHz) and 13C NMR (at 100MHz) spectroscopic data were recorded on an Avance 400 MHz spectrometer (BRUKER, Germany) in CDCl3. Gas chromatography-mass spectrometric (GC-MS) analyses were carried out with a Hewlett Packard 6890 & 5973 system (AGILENT, USA).

9-Bromonon-4-yne (5). Ammonia (500 mL) was condensed in a 1 L 2-necked flask attached to a circulating condenser maintained below -45 ℃. To the flask at -50 ℃, Fe(NO3)3·9H2O (713 mg, 1.76 mmol) was added to observe brown color at -50 ℃ and stirred it for 30 min. The lithium metal (2.47 g, 352.9 mmol) was added slowly to the mixture and the brown color was eventually turned into white-gray after additional 30 min stirring. Then, a solution of 1-pentyne (2) (17.4 mL, 176 mmol) in dry THF was added drop wise to the reaction mixture. The resulting solution was stirred for one hour, after which a solution of the 1,4-dibromobutane (3) (38.11 g, 176 mmol) in THF (70 mL) was added slowly. Stirring was continued for 2 h at -45 ℃ and the reaction mixture was left for stirring overnight at ambient temperature resulting in complete evaporation of ammonia. The residue was cautiously treated with saturated NH4Cl (200 mL) and then extracted with ether (3 × 250 mL). The combined organic layers was washed with water and dried over anhydrous Na2SO4. Removal of volatiles afforded a crude residue (34.1 g, mixture of 3, 9-bromonon-4-yne (5) and tetradeca-4,10-diyne (6)) under reduced pressure and these non-separable products were directly used in the next reaction. Products were confirmed by GC-MS analysis. GC-MS (m/z): 202 [M]+ (5), 216 [M]+ (3), and 190 [M]+ (6).

(Z)-9-Bromonon-4-ene (7). To a suspension of crude compound 5 (34.1 g, nearly 167.9 mmol) and 5% Pd/CaCO3 poisoned with lead (3.5 g, 1.67 mmol) was added quinoline (150 mg) in ethyl acetate (200 mL) and it was placed in Parr reaction bottle (500 mL). The reaction mixture was shaken under H2 atmosphere at 40 psi for 4 h using Parr hydrogenation apparatus. After completion of the reaction it was filtered through Celite and volatiles were removed in rotary evaporator under reduced pressure. The crude residue (34.0 g) (with mixture of products 3, (Z)-9-bromonon-4-ene (7) and (4Z,10Z)-tetradeca-4,10-diene (8)) that contain desired product was directly used in the next reaction. All the products were identified and confirmed by GC analysis. GC-MS (m/z): 204 [M]+ (7), 216 [M]+ (3), and 194 [M]+ (8).

(Z)-Tetradec-10-en-4-yn-1-ol (9). Again, ammonia (400 mL) was condensed in a 1 L 2-necked flask attached to a circulating condenser maintained below -45 ℃. To the flask, Fe (NO3)3·9H2O (670 mg, 1.66 mmol) was added to observe brown color and stirred for 30 minutes at -50 ℃. The lithium metal (4.17 g, 597 mmol) was added slowly to the mixture and the brown color was eventually turned into white-gray after additional 30 min stirring. Then, a solution of 4-pentyne-1-ol (4) (18.49 mL, 199 mmol) in dry THF (40 mL) was added drop wise to the reaction mixture. After an hour the mixture of compounds 3, 7, and 8 (34 g, 166 mmol) in dry THF (70 mL) was added drop wise to the flask. The reaction mixture was stirred for 1.5 h at -45 ℃ and then was left overnight at ambient temperature resulting in complete evaporation of the ammonia. The residue was cautiously treated with saturated NH4Cl (200 mL) and then extracted with ether (3 × 250 mL). The combined organic layers were Bull. Korean Chem. Soc. 2014, Vol. 35, No. 1 263 washed with water and dried on anhydrous NaSO4. The crude residue was purified using column chromatography (2:8 EtOAc/Hexane) to afford pure alkynol 9 (11.3 g, with overall yield 31% for three steps, purity by GC 99%) as a colorless liquid. IR νmax/cm-1: 3642 (w), 3011 (w), 2933 (s), 2849 (s), 2206 (s), 1552 (s), 1054 (s). 1H NMR: δ 0.96 (t, J = 7.3 Hz, 3H), 1.32-1.40 (m, 2H), 1.40-1.54 (m, 4H), 1.65 (br s, 1H), 1.70-1.77 (m, 2H), 1.97-2.08 (m, 4H), 2.12-2.18 (m, 2H), 2.25-2.31 (m, 2H), 3.76 (t, J = 5.0 Hz, 2H), 5.34-5.40 (m, 2H). 13C NMR: δ 13.78, 15.50, 18.66, 22.89, 26.75, 28.71, 28.98, 29.35, 31.75, 62.15, 79.42, 81.12, 129.80, 130.00. GC-MS m/z: 208 [M]+. Anal. Calcd. for C14H24O: C, 80.71; H, 11.61. Found: C, 81.02; H, 11.33.

(4E,10Z)-Tetradeca-4,10-dien-1-ol (10). Ammonia (200 mL) was condensed in a 500 mL 2-necked flask attached to a circulating condenser maintained below -45 ℃. To the flask at -50 ℃, it was added lithium metal (1.52 g, 217 mmol) giving a blue color on dissolution. The reaction mixture was kept under dry condition and stirred magnetically. After 30 min alkynol 9 (11.3 g, 54 mmol) in THF (50 mL) was added drop wise and stirred for 6 hours at -45 ℃. The reaction was left stirring for 4 hours at ambient temperature resulting in complete evaporation of ammonia. The residue was cautiously treated with saturated NH4Cl (100 mL) and then extracted with ether (3 × 100 mL). The combined organic layers were washed with water and dried with anhydrous NaSO4. The crude residue obtained was purified by column chromatography (using 3:7 EtOAc/Hexane) gave pure dienol, 10 (9.05 g, 79% yield, purity by GC > 98%) as a colorless liquid. IR νmax/cm-1: 3645 (w), 3005 (w), 2931 (s), 2853 (s), 1556 (s), 1050 (s), 969 (m). 1H NMR: . 0.90 (t, J = 7.3 Hz, 3H), 1.30-1.44 (m, 7H), 1.63 (m, 2H), 1.95-2.21 (m, 8H), 3.63-3.66 (m, 2H), 5.31-5.40 (m, 2H), 5.40-5.50 (m, 2H). 13C NMR: δ 13.78, 22.9, 27.10, 28.94, 29.21, 29.28, 29.35, 32.44, 32.58, 62.61, 129.55, 129.81, 129.95, 131.13. GCMS m/z 210 [M]+. Anal. Calcd. for C14H26O: C, 79.94; H, 12.46. Found: C, 80.22; H, 12.73.

(4E,10Z)-Tetradeca-4,10-dienyl acetate (1). To the dienol 10 (9.0 g, 43 mmol) in dry dichloromethane (100 mL), pyridine (6.78 mL, 85 mmol) was added at room temperature under nitrogen atmosphere. After stirring for 15 min., acetic anhydride (6 mL, 64 mmol) was added drop wise at 0 ℃. Reaction temperature was allowed to warm at RT and stirred for 3 h. After which 100 mL of water was added to the reaction mixture and was extracted with dichloromethane (2 × 100 mL). The combined organic layers were washed with water (2 × 100 mL), dried over NaSO4, filtered and concentrated under reduced pressure. Crude material was purified by column chromatography (using 1:9 EtOAc/Hexane) gave acetate 1 (10.5 g, 98% yield, purity by GC 96%) as a colorless liquid. IR νmax/cm-1: 3008 (w), 2931 (s), 2859 (s), 1742 (s), 1550 (s), 1239 (s), 1050 (s), 969 (m), 781 (m). 1H NMR: δ 0.90 (t, J = 7.3 Hz, 3H), 1.31-1.42 (m, 6H), 1.64-1.73 (m, 2H), 2.04 (s, 3H), 1.96-2.07 (m, 8H), 4.06 (t, J = 6.8 Hz, 2H), 5.33-5.37 (m, 2H), 5.37-5.50 (m, 2H). 13C NMR: δ 13.77, 20.93, 22.92, 27.11, 28.62, 28.90, 29.19, 29.29, 29.37, 32.44, 64.03, 128.83, 129.80, 129.95, 131.46, 171.05. GC MS (m/z): 252 [M]+. Anal. Calcd. for C16H28O2: C, 76.14; H, 11.18. Found: C, 75.40; H, 11.03.