Methyl-2-azido-3-[4'-(benzyloxy)-3'-methoxyphenyl]prop-2-enoate → Methyl 6-(benzyloxy)-5-methoxy-1H-indole-2-carboxylate

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A solution of the azidocinnamate (55) (12.2 g, 36.0 mmol) prepared as described in example 247 in xylene (300 mL) was added dropwise to refluxing xylene (100 mL) over 1.5 h, the reaction mixture was heated at reflux for a further 15 min and then most of the xylene was removed by distillation. The residue, on cooling to room temperature, formed a fine cream precipitate of methyl-6-(benzyloxy)-5-methoxyindole-2-carboxylate which was collected by filtration. The remaining xylene was removed from the mother liquor azeotropically with ethanol, the residue was recrystallized from ethanol to give further methyl-6-(benzyloxy)-5-methoxyindole-2-carboxylate. The mother liquor was again concentrated and the residue recrystallized. The methyl-6-(benzyloxy)-5-methoxyindole-2-carboxylate (56) (9.9 g total, 88%) was used in the next step without purification. Found: C, 69.38; H, 5.54; N, 4.55. C18H17NO4 requires: C, 69.44; H, 5.50; N, 4.50.

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