Practical synthesis of biaryl colchicinoids containing 3′,4′-catechol ether-based A-rings via Suzuki cross-coupling with ligandless palladium in water

Eight new biaryl colchicinoids containing 3′,4′-methylene or benzodioxy ether bridges were synthesized. The key synthetic step employed a ligandless, aqueous Suzuki cross-coupling reaction catalyzed by Pd(OAc)2 with tetrabutylammonium bromide (TBAB) and potassium carbonate (K2CO3). The biaryl Suzuki products were typically formed in 5–30 min and always in less than 1 h.