Cesium carbonate → 6-fluoro-1,1-dimethyl-7-nitro-2,3-dihydro-1H-pyrrolo[1,2-a]indole

Participants

Reaction Conditions

Reaction Steps

To a solution of 2-(4-(tert-butyldimethylsilyloxy)-2-methylbutan-2-yl)-6-fluoro-5-nitro-1H-indole (1.9 g, 5.0 mmol) and (S)-(2,2-dimethyl-1,3-dioxolan-4-yl)methyl 4-methylbenzenesulfonate (2.86 g, 10.0 mmol) in DMF (10 mL) was added Cs2CO3 (4.88 g, 15.0 mmol). The mixture was heated at 90° C. for 24 hours. The reaction was partitioned between ethyl acetate and water. The aqueous layer was extracted with ethyl acetate and the combined organic layers were washed with brine and dried over MgSO4. After the removal of solvent, the residue was purified by column chromatography (10-50% ethyl acetate-hexane) to afford 6-fluoro-1,1-dimethyl-7-nitro-2,3-dihydro-1H-pyrrolo[1,2-a]indole (600 mg, 48%). ESI-MS m/z calc. 248.1, found 249.2 (M+1)+. Retention time 2.00 minutes; 2-(4-(((R)-2,2-dimethyl-1,3-dioxolan-4-yl)methoxy)-2-methylbutan-2-yl)-1-(((R)-2,2-dimethyl-1,3-dioxolan-4-yl)methyl)-6-fluoro-5-nitro-1H-indole (270 mg, containing some (R)-2-(4-((2,2-dimethyl-1,3-dioxolan-4-yl)methoxy)-2-methylbutan-2-yl)-6-fluoro-5-nitro-1H-indole). ESI-MS m/z calc. 494.2 and 380.2, found 495.4 and 381.4 (M+1)+. Retention time 2.12 and 1.92 minutes; (R)-3-(1-((2,2-dimethyl-1,3-dioxolan-4-yl)methyl)-6-fluoro-5-nitro-1H-indol-2-yl)-3-methylbutan-1-ol (1.0 g, containing some 3-(6-fluoro-5-nitro-1H-indol-2-yl)-3-methylbutan-1-ol). ESI-MS m/z calc. 380.2 and 266.1, found 381.2 and 267.2 (M+1)+. Retention time 1.74 and 1.48 minutes.

Provenance & Evidence