2-Methyl-2-butene → HCID 21048654, compound

Participants

Reaction Steps

A solution of the alcohol 4-3 (210 mg, 0.528 mmol) in dichloromethane was treated with manganese dioxide (229 mg, 2.64 mmol) and heated to reflux where it remained for 1 h. Five additional equivalents of manganese dioxide were added and the reaction was maintained at reflux for 1 h. The excess manganese dioxide was filtered through Celite and the filter cake was washed with ethyl acetate (40 ml) and methanol (40 ml). The filtrate was concentrated in vacuo to a brown oil (4-4). A solution of the tert-butyl 5-formyl-2-(1H-indazol-3-yl)-1H-indole-1-carboxylate (4-4, 1.2 g, 3.3 mmol), 2-methyl-2-butene (19.9 ml, 188.2 mmol), a 1.9M solution of sodium phosphate monobasic (1.73 ml, 6.6 mmol), and sodium chlorite (597.3 mg, 6.60 mmol) were stirred in t-Butanol for 1 h. 3 additional equivalents of both solid sodium phosphate monobasic and sodium chlorite were added to the reaction over a 3 h period, and the reaction was mixed for 24 h. The t-Butanol was removed in vacuo and the residual yellow solid was dissolved in ethyl acetate (150 ml) and washed twice with a 98:2 mixture of 10% sodium bisulfite:10% potassium bisulfate (2×75 ml). The combined organics were dried over Na2SO4, filtered and concentrated in vacuo to afford 1-(tert-butoxycarbonyl)-2-(1H-indazol-3-yl)-1H-indole-5-carboxylic acid (4-5); 1H NMR(500 MHz, CDCl3) δ 8.47 (s, 1H), 8.40 (d, 1H, J=8.8 Hz), 8.17 (d, 1H, J=8.8 Hz), 7.68 (d, 1H, J=8.1 Hz), 7.56 (d, 1H, J=8.3 Hz), 7.46 (t, 1H, J=8.3 Hz), 7.23 (t, 1H, J=7.8 Hz), 6.99 (s, 1H), 1.14 (s, 3H).

Provenance & Evidence