1,1'-Carbonyldiimidazole → 1H-Indole-3-carboxylic acid 1-azabicyclo[3.2.1]oct-5-ylmethyl ester

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Reaction Steps

A solution of indole-3-carboxylic acid (1.45 g, 9 mmol) in anhydrous tetrahydrofuran (10 mL) under nitrogen was treated with 1,1'-carbonyldiimidazole (1.53 g, 9.4 mmol), stirred for one hour, and degassed with a stream of nitrogen over 10 minutes. Meanwhile, a cooled (-10° C.) solution of 1-azabicyclo[3.2.1]octane-5methanol (1.42 g, 10 mmol) in anhydrous tetrahydrofuran (10 mL) under nitrogen was treated (via syringe) with 2.5N n-butyllithium/hexane (9.7 mmol), stirred for 30 minutes, concentrated in vacuo, and taken up in anhydrous tetrahydrofuran (10 mL) under nitrogen. The acid 1,1'-carbonyldiimidazole adduct (suspension) was transferred into this solution, and the mixture was stirred overnight (18 hors) and concentrated in vacuo. The residue was partitioned between methylene chloride (100 mL) containing a little 2-propanol and saturated aqueous sodium carbonate (50 mL), and the organic layer was separated. The aqueous solution was extracted with methylene chloride (2×50 mL), and the combined organic solution was dried (Na2SO4), concentrated in vacuo and filtered through alumina (eluted with 5% methanol/methylene chloride). The concentrated filtrate was recrystallized from acetonitrile (2 crops) to afford 1.34 g (52%) of colorless solid; mp 183.5°-185.0° C.

Provenance & Evidence