Solvent‐Controlled Enzyme‐Catalyzed Friedel–Crafts Reactions of Indoles and Isatins by Using α‐Chymotrypsin

Friedel–Crafts reactions between isatins and indoles catalyzed by α‐chymotrypsin from bovine pancreas (BPC) are described. The reaction could be controlled by judicious choice of the solvent. 3‐Hydroxy‐oxindoles and 3,3‐bis(indol‐3‐yl)indolin‐2‐ones were obtained in aprotic (DCE) and protic solvent (MeOH), respectively; the reactions proceeded at 30 °C with a broad substrate scope in each case. Several pharmacologically active products were obtained in protic solvent. This method has the potential to become a simple, practical procedure for the synthesis of 3‐hydroxy‐oxindole and 3,3‐bis(indol‐3‐yl)indolin‐2‐one derivatives.