1,8-Diazabicyclo(5.4.0)undec-7-ene → Ethyl 2,4-dimethyl-3-pentenoate

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

Ethyl 2,4-dimethyl-3-pentenoate was prepared as follows. A 25 ml flask equipped with a condenser and kept under nitrogen, was charged with 1.0 g (6.4 mmole) of ethyl 2,4-dimethyl-2-pentenoate and 0.975 g (6.4 mmole) of DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), and the mixture was heated to 160° C. After 18 hours of reaction, followed by cooling, the reaction mixture was poured onto water and extracted with ether. The organic phase was washed successively with a 5% aqueous solution of HCI, water and brine, then dried on Na2SO4 and concentrated. After distillation on a bulb-to-bulb apparatus (80-100° C, 5.32 x 102 Pa) there were obtained 0,734 g of a 55:45 mixture of ethyl 2,4-dimethyl-2-pentenoate and ethyl 20 2,4-dimethyl-3-pentenoate. The two compounds were separated by flash-chromatography [SiO2 (30 g), cyclohexane:ethyl acetate =98:2]. 0.180 g of ethyl 2,4-dimethyl-3-pentenoate were obtained. NMR(1H): 1,19(d, J=7, 3H); 1,25(t, J=7, 3H); 1,66(d, J=1, 3H); 1,72(d, J=1, 3H)

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