N,N,N',N'-Tetramethylethylenediamine → 1',2'-Dihydrospiro[cyclopentane-1,3'-indole]-2'-one

Participants

Reaction Steps

To a −25° C. solution of oxindole (2.0 g, 15.0 mmol) in 40 (cm3) of anhydrous THF under N2 was added n-butyllithium (1.6 M in hexanes, 19.7 cm3, 31.5 mmol) drop-wise. To the resulting milky solution was added N,N,N′,N′-tetramethylethylenediamine (4.75 cm3, 31.5 mmol). After 30 min. a solution of 1,4-diiodobutane (21.9 g, 70.6 mmol) in THF (3 cm3) was added and the reaction mixture was allowed to warm to RT and stirred for 14 h. The reaction mixture was poured into water, extracted with EtOAc (×2), the combined organic layers were washed with dilute HCl (pH 1) and water (×2), dried (MgSO4) and evaporated. The residue was purified by column chromatography (SiO2, EtOAc:hexane 1:4) to afford the subtitled compound (1.4 g, 7.5 mmol, 50%) as a tan solid: 1H NMR (CDCl3) δ 1.8-2.2 (m, 8H), 6.94 (dd, J=7.5, 1.0 Hz, 1H), 7.01 (dd, J7.5, 1.0 Hz, 1H), 7.14-7.25 (m, 2H), 9.30 (br s, 1H).

Provenance & Evidence