2,3-Dichloro-5,6-dicyano-1,4-benzoquinone → 4-Acetyl-1-ethyl-6-methoxy-2-(4-methoxyphenyl)pyrrolo[2,1,5-cd]indolizine

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Reaction Steps

A solution of 1-ethyl-7-methoxy-2-(4-methoxyphenyl)indolizine (Compound 3) (2.0 g, 7.11 mmol) in 65 ml of toluene was stirred in an ice bath, while 3-butyn-2-one (0.64 ml, 8.17 mmol) was added dropwise. The cooling source was removed and stirring was continued for twenty hours. 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (1.73 g, 7.61 mmol) was added in portions and stirring was continued for twenty hours. The solvent was evaporated and the residue chromatographed over aluminium oxide with heptane/tetrahydrofuran (1:1) as eluent to afford 1.54 g (63%) of the title compound. M.p. 137-39° C. 1H-NMR (DMSO-d6, 200 MHz) δ: 1.39 (t, 3H), 2.64 (s, 3H), 3.15 (q, 2H), 3.87 (s, 3H), 4.09 (s, 3H), 7.19 (d, 2H), 7.80 (d, 2H), 7.82 (d, 1H), 7.89 (d, 1H), 8.15 (s, 1H). (Compound 6).

Provenance & Evidence