[N+](=[C:3]1[C:12](=[O:13])[C:11]2[C:6](=[CH:7][CH:8]=[C:9]([O:14][CH2:15][C:16]3[CH:21]=[CH:20][CH:19]=[CH:18][CH:17]=3)[CH:10]=2)[O:5][CH2:4]1)=[N-].[C:22]1([OH:28])[CH:27]=[CH:26][CH:25]=[CH:24][CH:23]=1>C1(C)C=CC=CC=1.C(OCC)(=O)C.CC(O)=O.CC(O)=O.CC(O)=O.CC(O)=O.[Rh].[Rh]>[CH2:15]([O:14][C:9]1[CH:10]=[C:11]2[C:6](=[CH:7][CH:8]=1)[O:5][CH2:4][CH:3]([O:28][C:22]1[CH:27]=[CH:26][CH:25]=[CH:24][CH:23]=1)[C:12]2=[O:13])[C:16]1[CH:21]=[CH:20][CH:19]=[CH:18][CH:17]=1A solution of 17 g of 3-diazo-6-benzyloxy-4-chromanone and 17 g of phenol in 100 ml of toluene was heated to 110° C. in an oil bath. Rhodium (II) acetate dimer (50 mg) was added in one portion. After nitrogen evolution ceased (5 minutes), the reaction was allowed to cool to room temperature, diluted with ethyl acetate and washed with 10% sodium hydroxide to remove excess phenol. The organic layer was dried over sodium sulfate and evaporated in vacuo to give the crude product, which was purified by column chromatography on silica gel elutinq with dichloromethane to give 2.6 g of product, m.p. 100-102° C.
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