General procedure for rhodium(II) acetate catalysed ylide formation and rearrangement. A solution of the α-diazo ketone (0.46 mmol) in CH 2 Cl 2 (60 mL) was added dropwise over 1.25 h to a stirred solution of rhodium(II) acetate dimer (2 mol%, 9 μmol) in CH 2 Cl 2 (45 mL) at room temperature under an atmosphere of argon. After addition was complete, the reaction mixture was concentrated in vacuo to give a green oil and the crude product was then purified by flash column chromatography on silica

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... gel. General procedure for copper(II) hexafluoroacetylacetonate catalysed ylide formation and rearrangement. A solution of the α-diazo ketone (0.46 mmol) in CH 2 Cl 2 (60 mL) was added dropwise over 1 h to a stirred solution of copper(II) hexafluoroacetylacetonate (2 mol%, 9 μmol) in CH 2 Cl 2 (45 mL) heated at reflux under an atmosphere of argon. After addition was complete, the reaction mixture was stirred for a further 30 min. Then the reaction mixture was concentrated in vacuo to a green oil and then purified by flash column chromatography.