Toluene → tert-butyl 2-(4-chloro-6,7-dihydro-5H-cyclopenta[b]pyridin-2-yl)-1H-pyrrole-1-carboxylate

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Reaction Conditions

Reaction Steps

A 20-mL sealed tube was charged with 2,4-dichloro-6,7-dihydro-5H-cyclopenta[b]pyridine (0.250 g, 1.33 mmol), 1-Boc-pyrrole-2-boronic acid (0.308 g, 1.46 mmol), tetrakis(triphenylphosphine)palladium(0) (0.076 g, 0.066 mmol), and Cs2CO3 (1.30 g, 3.99 mmol). Toluene (8 ml), EtOH (2 ml) and water (4 ml) were added. The resulting mixture was stirred under Ar at 90° C. for 23 h. After cooling to room temperature, the reaction solution was diluted with water (5 mL) and ethyl acetate (60 mL). The aqueous layer was separated and the organic layer was washed with saturated sodium chloride (5 mL) then dried over sodium sulfate, filtered, and concentrated under reduced pressure. The residue was purified by chromatography on silica using hexane/ethyl acetate (100:0 to 75:250) as eluent to afford tert-butyl 2-(4-chloro-6,7-dihydro-5H-cyclopenta[b]pyridin-2-yl)-1H-pyrrole-1-carboxylate (0.138 g, 32%) as a yellow oil. MW=318.80. 1H NMR (CDCl3, 500 MHz) δ 7.33 (dd, J=3.5, 2.0 Hz, 1H), 7.17 (s, 1H), 6.37 (dd, J=3.0, 2.0 Hz, 1H), 6.21 (t, J=3.5 Hz, 1H), 3.09 (t, J=7.5 Hz, 2H), 3.04 (t, J=7.5 Hz, 2H), 2.17 (quin, J=7.5 Hz, 2H), 1.38 (s, 9H). MS: ESI+, m/z 319 [M+H]+ and 4-chloro-2-(1H-pyrrol-2-yl)-6,7-dihydro-5H-cyclopenta[b]pyridine (0.077 g, 26%) as an off-white solid. MW=218.68. 1H NMR (CDCl3, 500 MHz) δ 9.63 (br s, 1H), 7.30 (s, 1H), 6.87-6.85 (m, 1H), 6.65-6.62 (m, 1H), 6.29-6.25 (m, 1H), 3.01 (t, J=7.5 Hz, 2H), 2.96 (t, J=7.5 Hz, 2H), 2.13 (quin, J=7.5 Hz, 2H); ESI MS m/z 218 [M]+.

Provenance & Evidence