3,3-Bis(5-methylfur-2-yl)-2-oxoindoline

To a boiling solution of isatine (3 g, 20 mmol) and sylvan (4 ml, 50 mmol) in 30 ml of dioxane one drop of 70% perchloric acid was added. The mixture was heated for 2 h and, after cooling, poured into 200 ml of H₂O. After washing by decantation, the brown oil was dissolved in 50 ml of ethanol. The precipitated product was recrystallised from dioxane to give 1.2 g (20%) of pale-rosy crystals.

M.p. 215-216deg.C.

¹H NMR (CDCl₃): 8.85-8.7 (s, 1H, NH), 7.4-6.75 (m, 4H, H_Ar), 6.1-6.0 (d, 2H, 3-H_Fur), 5.9-5.8 (d, 2H, 4-H_Fur), 2.15 (s, 6H, CH₃) ppm.

Anal. calc. for C₁₈H₁₅NO₃ (293.33): C 73.71, H 5.15, N 4.78; found: C 73.3, H 5.2, N 4.7.