Diisopropylamine → 3-Ethoxy-6-(3-t-butyldimethylsilyloxypropyl)cyclohex-2-enone

Participants

Reaction Conditions

Reaction Steps

To a lithium diisopropylamide (LDA) solution [prepared from diisopropylamine (3.82 mL, 27 mmol) and nBuLi (7.26 mL of a 2.5 M solution in hexanes, 18 mmol) in tetrahydrofuran (THF, 12 mL) at 0° C.] at −78° C. was added 3-ethoxy-2-cyclohexen-1-one (2.64 mL, 18 mmol) in THF (6 mL), dropwise, over 40 min. After stirring for an additional 30 min at −78° C., hexamethyl phosphoramide (HMPA, 3.16 mL, 18 mmol) was added followed by the dropwise addition of 3-iodo-1-tert-butyldimethylsiloxypropane (5.45 g, 18 mmol) in THF (8 mL). The resultant mixture was allowed to warm to rt, stirred for 6 h and then quenched by the addition of water (10 mL). The reaction mixture was then partitioned between dichloromethane (DCM, 100 mL) and sat. NH4Cl (40 mL). The aqueous phase was extracted with DCM (3×50 mL), the organic phases combined and washed with brine (50 mL), dried over anhydrous MgSO4 and reduced to dryness. The resultant syrup was purified by flash column chromatography (hexanes/EtOAc 8/2) to yield 2 as a pale yellow oil (2.92 g, 51.2%). Rf 0.21 (hexanes/EtOAc 8/2); 1H NMR (300 MHz, CDCl3) δ 5.26 (1H, s), 3.83 (2H, q, J=7.0 Hz), 3.59 (1H, t, J=6.5 Hz), 3.58 (H, t, J=6.5 Hz), 2.38 (2H, t, J=6.2 Hz), 2.20-1.99 (2H, m), 1.85-1.35 (5H, in), 1.31 (3H, t, J=7.0 Hz), 0.84 (s, 9H), 0.00 (s, 6H); 13C NMR (75 MHz, CDCl3) δ 201.6, 176.7, 102.3, 64.2, 63.4, 45.0, 30.5, 28.0, 26.4, 26.0 (x2), 18.4, 14.2, −5.2.

Provenance & Evidence