Ethyl 4-pentenoate → 2-Allyl-4-methyl-pent-4-enoic acid ethyl ester

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Reaction Steps

To a cold (−78° C.) stirred solution of LDA (generated from DIPA (1.42 mL, 10.14 mmol), BuLi (5.85 mL, 9.36 mmol) in THF at −78° C. for 20 min) in THF (31 mL) was added a solution of Pent-4-enoic acid ethyl ester (1.0 g, 7.8 mmol, 1.2 eq.) in THF (9.0 mL). After stirred for 1 h, neat 3-Bromo-2-methyl-propene (2.03 g, 15.0 mmol, 1.51 mL) was added and slowly warmed up to room temperature for overnight. The reaction mixture was then quenched with saturated NH4Cl solution, extracted with ether, washed with brine and dried. Evaporation of the solution furnished the 2-Allyl-4-methyl-pent-4-enoic acid ethyl ester (1.45 g, 100%) as an oil which was used in the next step without purification. 1H NMR (400 MHz, CDCl3), 5.78-5.71 (m, 1H), 5.05 (d, J=18.6 Hz, 1H), 5.02 (d, J=9.4 Hz, 1H), 4.76 (brs, 1H), 4.70 (s, 1H), 4.11 (dq, J=7.2, 1.0 Hz, 2H), 2.66-2.13 (m, 5H), 1.72 (s, 3H), 1.23 (dt, J=7.2, 1.3 Hz, 3H).

Provenance & Evidence