Ethyl (1α,8α,9α)-bicyclo[6.1.0]non-4-ene-9-carboxylate synthesis

Yield:79549-89-6 58% ，1263291-39-9 8.1%

Reaction Conditions:

with copper acetylacetonate in ethyl acetate;Reflux;

Steps:

To a solution of 1,5-cyclooctadiene (100 mL, 0.816 mol) and Cu(C₅H₇O₂)₂ (525 mg, 2 mmol) in EtOAc (50 mL) was added dropwise in 3 h a solution of ethyl diazoacetate (10.5 mL, 100 mmol) in EtOAc (50 mL). This solution was stirred overnight under reflux. EtOAc was evaporated and the excess of cyclooctadiene was removed by filtration over a glass filter filled with silica and elution with EtOAc:heptane, 1:200. The filtrate was concentrated in vacuo and the residue was purified by column chromatography on silica gel to afford endo-5 (3.5 g, 18%) and exo-5 (10.1 g, 58%) and mixed isomers (1.6g, 8.1%) as colorless oils. The rest of the synthesis was performed starting with exo-5 as published.^{3 1}H-NMR (400 MHz): (CDCl₃) δ: 5.53 (m,1H), 3.90-3.88 (d, 2H), 3.55-3.44 (m, 8H), 3.30 (m, 2H), 2.33-2.05 (m, 8H), 1.28 (m, 2H), 0.67-0.58 (m, 3H) ¹³C-NMR (100 MHz): (CDCl₃) δ: 156.88, 98.75, 73.00, 70.23, 70.14, 70.12, 68.93, 41.49, 40.72, 33.26, 23.73, 22.79, 21.36 HRMS: [M+H]⁺:m/z 325.21157 (calculated: 325.21218)

References:

Gential, Geoffroy P.P.;Ho, Nataschja I.;Chiodo, Fabrizio;Meeuwenoord, Nico;Ossendorp, Ferry;Overkleeft, Herman S.;van der Marel, Gijs A.;Filippov, Dmitri V. [Bioorganic and Medicinal Chemistry Letters,2016,vol. 26,# 15,p. 3641 - 3645] Location in patent:supporting information