General procedure for the synthesis of O-THP propargyl alcohol (Compound 18) from 3,4-dihydro-2H-pyran and 2-propyn-1-ol: Compound 18 was prepared according to literature procedure. To a solution of propargyl alcohol 17 (2.6 mL, 44.6 mmol) and p-toluenesulfonic acid monohydrate (0.09 g, 0.5 mmol) in dichloromethane (45 mL) was added dropwise 3,4-dihydro-2H-pyran (4.3 mL, 46.8 mmol) at 0 °C. The reaction mixture was stirred at 0 °C for 5 min before slowly warming up to room temperature and continued stirring for 1 h. The reaction mixture was then purified with aqueous solution of saturated 2H-pyran (4.3 mL). Subsequently, the reaction mixture was washed with saturated sodium bicarbonate solution (30 mL) and the aqueous layer was extracted with dichloromethane (45 mL). The organic layers were combined, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to give compound 18 (6.1 g, 97.2% yield) as a yellow oil. Thin layer chromatography (TLC) Rf = 0.30 (hexane/ether, 95:5). 1H NMR (400 MHz, CDCl3): δ = 1.50-1.67 (m, 4H), 1.70-1.89 (m, 2H), 2.41 (t, J = 2.4 Hz, 1H), 3.52-3.57 (m, 1H), 3.82-3.87 (m , 1H), 4.27 (ddd, J = 2.4 Hz, 11.3 Hz, 15.8 Hz, 2H), 4.83 (t, J = 3.4 Hz, 1H). 13C NMR (100 MHz, CDCl3): δ = 19.0, 25.3, 30.2, 53.9, 61.9, 74.0, 79.7, 96.8. mass spectra (MS-CI): m/z calculated values. ): m/z calculated value C8H12O2 [M + H]+, 141; measured value: 141. The synthesis of this compound has been reported in the literature.
