Defluorinative Ring‐Opening Indolylation of Siloxydifluorocyclopropanes: Controlled Synthesis of α‐Fluoro‐β‐Indolyl‐Propanones for Carbazole Construction

Abstract A catalytic defluorinative ring‐opening indolylation of siloxydifluorocyclopropanes was reported. It was found that AgBF 4 ‐catalyzed reaction of siloxydifluorocyclopropanes with indoles could be controlled to deliver α‐fluoro‐β‐indolyl‐propanones within 1.5 hours at room temperature. Cyclization of these α‐fluoroketone derivatives were then carried out in the presence of trifluoroacetic anhydride in toluene at room temperature. Carbazoles were formed efficiently via an intramolecularly nucleophilic addition of the in situ formed enamine intermediate to the keto carbonyl, followed by a sequential hydrolysis and eliminations of trifluoroacetic acid and hydrogen fluoride. magnified image