New Synthesis of 3-Substituted Indazoles from 3-Trimethylsilylindazole

Abstract

Reaction of aryl aldehydes with 3-trimethylsilylindazole in the presence of CsF easily gave the corresponding 3-(arylhydroxymethyl)indazoles in good to moderate yields.

Keywords

aryl aldehydes - Brook rearrangement - cesium fluoride - indazoles - silyl compounds

References

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8

No reaction occurred at r. t.

9

In fact, in the reaction of 3-trimethylsilylindazole(1) with PhCHO, the use of K₂CO₃ in place of CsF as a base gave the desired product 5a (58 %) together with indazole(4) (37 %). Reaction conditions: PhCHO (10 equiv), K₂CO₃ (1.5 equiv), MS 3Å, DMF, 80 °C, 6 h.

10

Probably, the Brook rearrangement giving the irreversible O-silyl intermediate 8 would accelerate this reaction.