3-Alkylated indoles by reduction of sulfonyl indoles under flow chemical conditions

Reduction of 3-(1-arylsulfonylalkyl) indoles (sulfonyl indoles) using polymer-supported sodium borohydride under flow chemical conditions allows an efficient synthesis of 3-alkylindoles with a notable waste minimization and reduced solvent consumption. The flow conditions can be also applied to the synthesis of sulfonyl indoles which can be obtained by a three-component coupling of indoles with aldehydes and p-toluenesulfinic acid. Using the two-step flow chemical approach, 3-alkylindoles can be directly obtained from their remote indole and aldehyde precursors. [GRAPHICS] .