Acetic Anhydride → Ethyl 2-ethylidene-6-methyl-5-heptenoate

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Reaction Steps

A mixture of ethyl 2-(4-methyl-3-pentenyl)-3-hydroxybutyrate (23.0g, 0.107 mol), acetic anhydride (14.28g, 0.14 mol), dimethylaminopyridine (0.714g, 0.0058 mol), 1,8diazabicyclo[5.4.0]undec-7-ene (42.5g, 0.28 mol) and toluene (250 mL) was heated in a stainless steel autoclave at 110° C. for 4h and then at 150° C. for 6h. The mixture was cooled, washed sequentially with water (50 mL), 2N HCl (3×50 mL), sodium bicarbonate solution until neutral, and dried (sodium sulfate). The solvent was evaporated and the residue distilled to provide 9.93g of ethyl 2-ethylidene-6-methyl-5-heptenoate (GLC purity 94%, about an 8:1 mixture of E:Z isomers). NMR (CDCl3 60 MHz) δ 1.28 (3H, t, J=7Hz, 1.62 (3H, s), 1.68 (3H, s), 1.80 (3H, d, J=7Hz), 1.6-2.4 (4H, m), 4.21 (2H, q, J=7Hz), 4.9-5.3 (1H, m), 6.87 (1H, q, J=7Hz), IR 2960, 2910, 1715, 1640, 440, 1370, 1270 cm-1 ; MS m/e 196, 167, 150, 69.

Provenance & Evidence