Unexpectedly superior efficiency of chloride-directed double Suzuki–Miyaura cross-coupling reactions to bromide-directed reactions for the synthesis of sterically hindered 2,7-diaryl fluorenes

Abstract

Sterically hindered 2,7-diaryl fluorenes have been efficiently synthesized via double Suzuki–Miyaura cross-coupling reactions of challenging 2,7-dichlorofluorene with a broad range of di-ortho-substituted arylboronic acids using the N-heterocyclic carbene Pd catalyst INPd. The efficiency of chloride-directed reactions is superior to that of bromide-directed reactions. Mechanistic studies revealed a tandem process for the double Suzuki–Miyaura cross-coupling reaction.