Preparative Scale Stereoselective Synthesis of Methyl 4-Methyl-(Z)-2, 4-Pentadienoate

One-Pot Transformation of Silyl Enol Ethers into 1,3-Dienes: In situ Generation of Alkenyl Nonaflates and Subsequent Heck Reactions − Scope and Limitations

“…Methyl ( E )‐4‐Methylpenta‐2,4‐dienoate (28): Nonaflation of silyl enol ether 1i (0.261 g, 2.00 mmol) with NfF (0.785 g, 2.60 mmol) was performed in THF (1 mL) with KF (0.120 g, 2.07 mmol) and dibenzo‐18‐crown‐6 (0.144 g, 0.40 mmol) at 25 °C for 120 h according to GP2 . After addition of LiCl (0.127 g, 3.00 mmol), Et 3 N (0.405 g, 4.00 mmol), Pd(OAc) 2 (0.022 g, 0.10 mmol), methyl acrylate (0.224 g, 2.60 mmol) and DMF (1 mL), the mixture was stirred at 25 °C for 17 h, followed by the usual workup ( n ‐pentane) and CC ( n ‐pentane/Et 2 O, 25:1), to provide 28 37 (0.080 g, 30% yield) as a slightly yellowish oil. 1 H NMR (270 MHz, CDCl 3 ): δ = 1.89 (dd, J = 1.3, 1.0 Hz, 3 H, Me), 3.76 (s, 3 H, CO 2 Me ), 5.34−5.37 (m, 2 H, 5‐H), 5.88 (d, J = 15.8 Hz, 1 H, 2‐H), 7.37 (dd, J = 15.8, 0.5 Hz, 1 H, 3‐H) ppm.…”