Cesium carbonate → Tert-butyl 2-phenylsulfonyl-5-methyl-5,6,7,8,9,10-hexahydro-7,10-epiminocyclohepta[b]indole-carboxylate

Participants

Reaction Steps

A mixture of product from step B (1.5 g, 3.84 mmol) and benzene sulfinic acid sodium salt (755 mg, 4.6 mmol) were suspended in toluene (30 mL) and N2 was bubbled through the reaction mixture for 10-15 min. Di-palladium-tris(dibenzylideneacetone) (89 mg, 0.096 mmol), cesium carbonate (1.84 g, 5.76 mmol), xantphos (111 mg, 0.192 mmol) and tetrabutylammonium chloride (1.28 g, 4.6 mmol) were then added sequentially, and the reaction was heated to reflux for 12 h. The reaction mixture was cooled to ambient temperature, partitioned between ethyl acetate and sat. ammonium chloride solution and the organics removed. The aqueous was extracted with ethyl acetate (×2) and the combined organics dried over sodium sulfate and concentrated. Purification by flash column chromatography (silica gel, hexanes/EtOAc, 100:0 to 50:50) provided tert-butyl 2-phenylsulfonyl-5-methyl-5,6,7,8,9,10-hexahydro-7,10-epiminocyclohepta[b]indole-carboxylate (1.22 g, 71%) as a yellow solid: 1H NMR (300 MHz, CDCl3) δ 8.20 (s, 1H), 7.96 (dd, J=7.7, 1.5 Hz, 2H), 7.68 (d, J=9.0 Hz, 1H), 7.47 (m, 3H), 7.30 (d, J=8.7 Hz, 1H), 5.25 (brs, 1H), 4.68 (m, 1H), 3.60 (s, 3H), 3.37 (m, 1H), 2.50 (d, J=16.7 Hz, 1H), 2.26 (m, 2H), 1.94 (t, J=10.3 Hz, 1H), 1.61 (m, 1H, partially masked by H2O peak), 1.36 (s, 9H).

Provenance & Evidence