One-pot Synthesis of Dibenzofurans via SNAr and Subsequent Ligand-free Palladium-catalyzed Intramolecular Aryl-aryl Cross-coupling Reactions under Microwave Irradiation

Abstract

Dibenzofuran derivatives, besides their uses for molecular recognition [1 – 3], catalytic reactions [4, 5] and metal-binding sites [6], also display interesting biological activities, such as against the human immunodeficiency virus (HIV)-1 [7] and for protein tyrosine phosphatase 1B (PTP1B) inhibition [8]. Therefore, much attention has been paid to the construction of dibenzofurans. Ames et al. reported the synthesis of dibenzofurans, but step-wise procedures were needed there, and the yields were usually low [9]. Although dibenzofurans could also be prepared by the reaction of ortho-iodophenols with silylaryl triflates in the presence of CsF and palladium, expensive excess base and other not easily available starting materials were needed [10]. Another innovative route for the synthesis of substituted dibenzofurans has been described by Goel et al., however, special starting materials must be used for this tedious procedure [11]. In our previous work, we have reported a one-pot synthesis of dibenzofurans directly from 2-bromophenols with aryl halides via an SNAr reaction and subsequent palladium-catalyzed intramolecular aryl-aryl coupling