(Z)-1-Methoxy-2-Methylseleno-1-(Trimethylsiloxy)Propene

Abstract

[868617-71-4] C8H18O2SeSi (MW 253.27) InChI = 1S/C8H18O2SeSi/c1-7(11-3)8(9-2)10-12(4,5)6/h1-6H3/b8-7- InChIKey = YUIWJVQHUUQPBG-FPLPWBNLSA-N (reagent used as a nucleophile in asymmetric synthesis of organic compounds) Physical Data: bp 31 °C/0.4 mmHg; d 1.178 g cm−3. Solubility: sol alcohol, ether, and most organic solvents. Form Supplied in: a pale yellow oil; commercially unavailable. Analysis of Reagent Purity: IR (neat): 1724, 1655, 1439, 1252, 1221, 1178, 1132, 1097, 901, 843 cm−1; 1H NMR (C6D6): δ 3.30 (s, 3H), 2.13 (s, 3H), 1.87 (s, 3H), 0.30 (s, 9H); 13C NMR (C6D6): δ 152.8, 84.0, 56.0, 17.4, 4.5, 0.2; HR MS: calcd. for C8H18O2SeSi (M+) 254.0241, found 254.0240. Preparative Methods: (1) (eq 1; Step 1) To a suspension of selenium powder (7.0 g, 89 mmol) in THF (177 mL) at 0 °C was added methyllithium in ether (0.98 M, 98 mL, 96 mmol). After the reaction mixture had been stirred for 30 min at 0 °C, methyl 2-bromopropanoate (9.9 mL, 89 mmol) was added to the mixture at −78 °C. The reaction mixture was allowed to warm to room temperature and then saturated aqueous ammonium chloride was added. The mixture was extracted with diethyl ether, and the organic layer was washed with water and brine, dried over sodium sulfate. After filtration of the mixture and evaporation of the solvent, the crude product was purified by distillation to afford methyl 2-methylselenopropanoate (13.3 g, 82%) as a pale yellow oil: bp 82 °C/65 mmHg; IR (neat): 1730 cm−1;1H NMR (CDCl3): δ 3.68 (s, 3H), 3.41 (q, J = 7.3 Hz, 1H), 2.06 (s, 3H), 1.49 (d, J = 7.3 Hz, 3H); 13C NMR (CDCl3): δ 174.0, 52.0, 31.7, 16.9, 3.9; HR MS: calcd. for C5H10O2Se (M+) 181.9846, found 181.9843. (eq 1; Step 2) To a solution of diisopropylamine (1.8 mL, 12.8 mmol) in THF (15 mL) at 0 °C was added n-butyllithium in hexane (1.66 M, 7.8 mL, 12.9 mmol). After the reaction mixture had been stirred for 30 min at 0 °C, a solution of methyl 2-methylselenopropanoate (2.13 g, 11.8 mmol) in THF (10 mL) was added at −78 °C. The reaction mixture was stirred for 1 h at −78 °C and then chlorotrimethylsilane (3.0 mL, 23.7 mmol) was added. After the reaction mixture had been stirred for 1 h at room temperature, it was concentrated by evaporation of the solvent. Petroleum ether was added to the residue, and the suspension was filtered through a short pad of Celite under an argon atmosphere. After evaporation of the solvent, the crude product was purified by distillation to afford a mixture of (Z)- and (E)-1-methoxy-2-methylseleno-1-(trimethylsiloxy)propene (Z/E = 90/10, 2.22 g, 75%). Purification: usable after distillation. Handling, Storage, and Predictions: stable after distillation under argon or nitrogen atmosphere.