Multicomponent Reaction for Diastereoselective Synthesis of Spiro[carbazole-3,4 '-pyrazoles] and Spiro[carbazole-3,4 '-thiazoles]

In the presence of copper sulfate, the three-component reaction of aromatic aldehydes, ethylindole-3-acetate and 4-arylidene-5-methyl-2-phenylpyrazol-3-ones, in refluxing toluene afforded spiro[carbazole-3,4'-pyrazoles] in good yields with high diastereoselectivity. More importantly, the similar CuSO4 promoted the four-component reaction of two molecular aromatic aldehydes with ethylindole-3-acetate and 5-methyl-2-phenyl-pyrazol-3-one resulted in 2,4-diarylspiro[carbazole-3,4'-pyrazoles] in satisfactory yields. Additionally, CuSO4 promoted the four-component reaction of two molecular aromatic aldehydes, ethylindole-3-acetate and 2-phenylthiazol-4-one, in refluxing toluene gave 2,4-diarylspiro[carbazole-3,4'-thiazoles] with diastereomeric ratios in the range of 3:1 to 20:1.

Automated summary

The presence of copper sulfate enables the three-component and four-component reactions involving aromatic aldehydes, ethylindole-3-acetate, and various small molecules to proceed efficiently in refluxing toluene, yielding spiro[carbazole-3,4'-pyrazoles] and spiro[carbazole-3,4'-thiazoles] with high diastereoselectivity. The reaction outcomes demonstrate the versatility and potential utility of CuSO4 catalysis in diverse multi-component reactions.