Dimethyl methylphosphonate → dimethyl(S)-(3-methyl-2-oxo-6-phenylhexyl)phosphonate

Participants

Reaction Steps

To a stirring solution consisting of dimethyl methylphosphonate (23.37 g, 188.4 mmol) in THF (400 mL) at −78° C. was slowly added n-butyllithium solution (112 mL, 179 mmol, 1.6 M solution in hexane). The reaction mixture was stirred for 30 minutes, after which time, (S)-(+)-ethyl 2-methyl-5-phenylpentanoate (14mb(i), 28.1 g, 94.2 mmol) in THF (100 mL) was slowly added. The resulting reaction mixture was stirred at −78° C. for two hours and was then allowed to rise to room temperature overnight. The reaction mixture was treated with 5% KHSO4 and extracted with ethyl acetate three times. The organic layer was washed twice with 50:50 water-brine and the organic layer was dried over sodium sulfate, filtered, and concentrated under vacuum. The residue was purified by silica gel chromatography. Elution with ethyl acetate-heptane (60:40 v/v) afforded the title compound (11.9 g, 42%) as a clear oil, pure of unrelated components; TLC Rf 0.22 (solvent system: 60:40 v/v ethyl acetate-heptane); HPLC retention time 14.5 minutes, 5μ Chiralpak IA 250×4.6 mm, ultraviolet detector at 210 nm, 1 mL/min, chiral purity 97.8% (S), 2.19% (R); MS (ESI−) m/z 297.1 (M−H)−; 1H NMR (CDCl3) δ 7.28-7.21 (m, 2H), 7.17-7.12 (m, 3H), 3.76-3.71 (m, 6H), 3.10 (d, J=2.20 Hz, 1H), 3.04 (d, J=2.20 Hz, 1H), 2.79-2.70 (m, 1H), 2.54-2.62 (m, 2H), 1.74-1.54 (m, 3H), 1.42-1.24 (m, 1H), 1.07 (d, J=6.96 Hz, 3H); [α]Tλ=α/cl, [α]21.9D=+0.084/(0.0169 g/1.5 mL)(0.5)=+14.91° (c=1.13, CHCl3).

Provenance & Evidence