Sodium hydride → (3Z)-3-(4,4-dimethyl-2-oxopentylidene)spiro[bicyclo[2.2.1]heptane-7,1'-cyclopropan]-2-one

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Reaction Conditions

Reaction Steps

A solution (4,4-dimethyl-2-oxo-pentyl)-phosphonic acid dimethyl ester (1.249 g) in THF (40 ml) was cooled to 0° C. under an argon atmosphere and sodium hydride (0.268 g) was added in 4 portions. Spiro[bicyclo[2.2.1]heptane-7,1′-cyclopropane]-2,3-dione (1.023 g) dissolved in THF (30 ml) was then added dropwise to the reaction mixture. The mixture was then stirred for further 15 minutes at 0° C. (until completion of reaction according to TLC analysis). The reaction mixture was partitioned between water/3N HCl and AcOEt, the layers were separated, the organic layer washed with saturated, aqueous NaCl, dried over Na2SO4, filtered and evaporated. The residue was purified by flash chromatography with heptane/AcOEt: 100% to 95% as eluant to give (3E)-3-(4,4-dimethyl-2-oxopentylidene)spiro[bicyclo[2.2.1]heptane-7,1′-cyclopropan]-2-one (0.284 g) and (3Z)-3-(4,4-dimethyl-2-oxopentylidene)spiro[bicyclo[2.2.1]heptane-7,1′-cyclopropan]-2-one (0.287 g) as yellow oils, respectively, that were directly used in the next step. Assignment of the E/Z isomers was done by NMR.

Provenance & Evidence