N-Methylcarbazole → 7-tert-butyl-5-methyl-3-(9-methyl-9H-carbazol-3-yl)-3H-benzofuran-2-one

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Reaction Steps

A mixture of 2.2 g (10.0 mmol) of 7-tert-butyl-3-hydroxy-5-methyl-3H-benzofuran-2-one (compound (202), Example 1a, Table 2), 1.8 g (10.0 mmol) of N-methylcarbazole and 0.2 g of Fulcat 22B and 20 ml of n-octane is refluxed for 5 hours under nitrogen. The Fulcat 22B catalyst is subsequently removed by filtration and excess n-octane is distilled off on a vacuum rotary evaporator. Chromatography of the residue on silica gel with the solvent system dichloromethan/hexane=1:2 to 1:1 and subsequent crystallisation of the pure fractions from methanol yields 0.70 g (10%) of 7-tert-butyl-5-methyl-3-(9-methyl-9H-carbazol-3-yl)-3H-benzofuran-2-one, m.p. 84°-90° C. (compound (120), Table 1). The product may additionally contain minor amounts of other structural isomers in accordance with the substitution at the carbazole ring.

Provenance & Evidence