Diisopropylethylamine → Tert-butyl 5-azaspiro[2.4]heptane-5-carboxylate

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Reaction Steps

5-Aza-spiro[2.4]heptane-5,6-dicarboxylic acid 5-tert-butyl ester (350 mg, 1.45 mmol) was mixed with HATU (551 mg, 1.45 mmol) in DMF (5 mL) and the mixture was stirred at room temperature for 30 minutes. 2-Amino-1-(4-bromo-phenyl)-ethanone bis HCl salt (416 mg, 1.45 mmol) in 2 mL DMF was added, followed by DIEA (3.5 eq., 0.88 mL) dropwise at 0° C. The reaction was stirred at 0° C. for 40 minutes. The reaction mixture was diluted in ethyl acetate and washed with saturated sodium bicarbonate solution. The organic layer was dried (MgSO4), concentrated and purified by flash column chromatography (silica gel, 20 to 100% ethyl acetate/hexane) to give 642-(4-Bromo-phenyl)-2-oxo-ethylcarbamoyl]-5-aza-spiro[2.4]heptane-5-carboxylic acid tert-butyl ester (424 mg, 67%). LCMS-ESI−: calc'd for C20H25BrN2O4: 437.33. Found: 460.1 (M+Na+). 6-[5-(4-Bromo-phenyl)-1H-imidazol-2-yl]-5-aza-spiro[2.4]heptane-5-carboxylic acid tert-butyl ester: 15 mL Xylenes was added to 642-(4-Bromo-phenyl)-2-oxo-ethylcarbamoyl]-5-aza-spiro[2.4]heptane-5-carboxylic acid tert-butyl ester (424 mg, 0.97 mmol) and ammonium acetate (20 eq., 1.5 g). The mixture was heated in microwave at 140° C. for 60 minutes. The mixture was diluted with EtOAc and washed with sat.NaHCO3 aqueous solution. The organic layer was concentrated down and purified by flash column chromatography (silica gel, 20 to 80% ethyl acetate/hexane) to give 6-[5-(4-Bromo-phenyl)-1H-imidazol-2-yl]-5-aza-spiro[2.4]heptane-5-carboxylic acid tert-butyl ester (249 mg, yield 61%). LCMS-ESI−: calc'd for C20H24BrN3O2: 418.33. Found: 418. (M+H+).

Provenance & Evidence