Methanol → 3-(1,1-dimethoxy-methyl)-6-iodo-1-(2-trimethylsilanyl-ethoxymethyl)-1H-indazole

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Reaction Steps

A solution of 6-iodo-3-styryl-1-[2-(trimethyl-silanyl)-ethoxymethyl]-1H-indazole [Example 14, step (i)] (1.28 g, 2.69 mmol) in CH2Cl2 (40 mL)/MeOH (40 mL) was stirred at −78° C. The reaction was treated with ozone until a blue color persisted, and then was purged with argon. Methyl sulfide (4 mL) was added, and the reaction stirred 4 h while warming to r.t. Concentration in vacuo gave a crude mixture of acetal and aldehyde, which was converted completely to the acetal by stirring in trimethyl orthoformate (10 mL) with Amberlyst 15 (wet) acidic ion-exchange resin (0.8 g) for 1 h. The resin was removed by filtration, and the solution was concentrated in vacuo. Purification by silica gel chromatography gave 1.11 g (92%) of 3-(1,1-dimethoxy-methyl)-6-iodo-1-(2-trimethylsilanyl-ethoxymethyl)-1H-indazole as a clear oil. 1H NMR (300 MHz, CDCl3) δ 7.98 (s, 1H), 7.68 (d, 1H, J=8.4 Hz), 7.48 (dd, 1H, J=8.4, 1.2 Hz), 5.77 (s, 1H), 5.69 (s, 2H), 3.53 (t, 2H, J=8.4 Hz), 3.43 (s, 6H), 0.88 (t, 2H, J=8.4 Hz), −0.06 (s, 9H).

Provenance & Evidence