Nitrogen → (R)-4-(hex-3-ynyl)-2,2-dimethyl-1,3-dioxolane

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

To a flask cooled to −78° C. under N2 was added 2-butyne gas via syringe needle until approximately ˜3 mL of liquid had condensed in the flask. THF (120 mL) was then added followed by DMPU (18.9 ml, 156 mmol). The flask was purged with N2 and n-butyllithium (2.5M hexanes, 18.7 ml, 46.9 mmol) was added via syringe over 5 min and stirred for an additional 15 min at which time (R)-4-(2-iodoethyl)-2,2-dimethyl-1,3-dioxolane (10.0 g, 39.1 mmol) was added as a solution in THF (30 mL) [preparation of enantiopure (R)-4-(2-iodoethyl)-2,2-dimethyl-1,3-dioxolane from commercially available (R)-2-(2,2-dimethyl-1,3-dioxolan-4-yl)ethanol was performed using the procedure described by: Taber. D. F.; Xu, M.; Hartnett, J. C. J. Am. Chem. Soc. 2002, 124, 13121]. The reaction was slowly warmed to rt and stirred a total of 3 h. The mixture was quenched with sat. NH4Cl, and extracted with Et2O (2×). The organics were washed with H2O, and brine, dried over MgSO4, filtered, and concentrated. The material was purified by silica gel chromatography (5% EtOAc in hexanes gradient to 15% EtOAc in hexanes) to give (R)-4-(hex-3-ynyl)-2,2-dimethyl-1,3-dioxolane as a clear oil. 1H NMR (400 MHz, CDCl3): δ 4.19 (1H, m), 4.08 (1H, dd, J=8.0, 6.0 Hz), 3.58 (1H, dd, J=7.6, 6.8 Hz), 2.26 (2H, m), 2.15 (2H, qt, J=5.2, 2.4 Hz), 1.81 (1H, m), 1.68 (1H, m), 1.40 (3H, s), 1.36 (3H,s), 1.11 (3H, t, J=7.6 Hz).

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