Dichloromethane → ethyl 2-hydroxy-2-methylpent-4-enoate

Ethyl 2-oxopropanoate (1 g, 8.61 mmol) was taken in to DCM (5M) and cooled to −78 C. To this titanium tetrachloride (8.61 mL, 8.61 mmol) in dichloromethane (5 mL) was added and stirred the reaction mixture for 30 min at this temperature. To this reaction mixture allyltrimethylsilane (1.279 g, 11.20 mmol) was added drop wise at −78° C. and stirring was continued for 2 h. Then it was brought to 0° C. and quenched with saturated aq. sodium bicarbonate solution and stirred for 15 min, and filtered through celite bed and filtrate was evaporated under reduced pressure to afford colorless oil. The residue was purified by flash chromatography (silica, 230-400, 10% EtoAc/Pet ether) to obtain ethyl 2-hydroxy-2-methylpent-4-enoate B-37a (0.8 g, 5.06 mmol, 58.7% yield) as yellow liquid. 1H NMR (CDCl3, δ=7.26 ppm, 400 MHz): δ 5.84-5.72 (m, 1H), 5.15-5.09 (m, 2H), 4.29-4.19 (m, 2H), 2.56-2.37 (m, 2H), 1.43 (s, 3H), 1.31 (t, J=9.6 Hz, 3H).