Microwave-accelerated Suzuki cross-coupling reaction in polyethylene glycol (PEG)

Abstract

Polyethylene glycol (PEG) is found to be an inexpensive and non-toxic reaction medium for the microwave-assisted Suzuki cross-coupling of arylboronic acids with aryl halides. This environmentally friendly microwave protocol offers ease of operation and enables recyclability of catalyst and synthesis of a variety of substituted biaryls employing palladium chloride as catalyst and potassium fluoride as the base.

Atom‐Efficient, Palladium‐Catalyzed Stille Coupling Reactions of Tetraphenylstannane with Aryl Iodides or Aryl Bromides in Polyethylene Glycol 400 (PEG‐400)

“…[8] PEG as an environmentally benign protocol proved to have many particular applications, such as in coupling, [9] substitution, [10] oxidation, [11] addition, [12] and reduction reactions. [13] To the best of our knowledge, the palladiumcatalyzed atom-efficienct Stille cross-coupling reaction of tetraphenylstannane in PEG-400 has not so far been reported.…”

Recent applications of the Suzuki–Miyaura cross-coupling reaction in organic synthesis

“…They later used the same strategy to synthesise 1H-benzimidazoles, 1H-imidazo [4,5-b]pyridines 107 and 1H-imidazo [4,5-c]pyridines. 108 Varma 109 investigated the effect of various bases on the PEG-based coupling reaction in the presence of microwave irradiation (Scheme 47) and found KF to be the most convenient protocol. The use of other bases requires water as the co-solvent for their dissolution, which not only reduces the solubility of the aromatic halides but also increases the self-coupling products of the boronic acids.…”

A Microwave‐Assisted Heck Reaction in Poly(ethylene glycol) for the Synthesis of Benzazepines

“…So far, PEGs have not been used extensively in reactions involving microwave activation. [24][25][26][27][28][29][30][31][32][33][34][35] We now report that novel benzazepines can be obtained by a palladium-catalysed Heck reaction in a PEG solvent under microwave heating.…”