Aryl continuous-flow Suzuki-Miyaura

Finally, the Suzuki-Miyaura reaction, which has become one of the most versatile and important reactions for the construction of C-C bonds, could be performed in a continuous flow process under ligand-free conditions [43]. The PASSfiow reactor is suited for the coupling of 4-iodoacetophenone and other aryl halides with arylboronic acid to yield the corresponding diaryls within 3 h without formation of homocoupling by-products (Scheme 15). After collecting... 

Buchwald and co-authors reported synthesis of biaryls by a lithiation/ borylation/Suzuki-Miyaura cross coupling sequence in continuous flow [53]. Aryl bromides could be lithiated at room temperature with 2 s-10 min residence time by mixing with n-BuLi, which then reacted with B(OiPr)3 at room temperature with 1 min residence time to afford aryl borates, ArB(OiPr)3Li. The reactor was sonicated to avoid blocking by precipitated ArB(OiPr)3Li. The reaction mixture was then mixed with Pd catalyst/THF solution and reacted at 60 °C (4—10 min residence time) to give biaryls in good yields. For example, 2-fluoro-4 -methoxy-[l,l -biphenyl]-4-carbonitrile was obtained in 94% yield (4 min residence time) (Scheme 5.38). 

The nature of ligands, such as Boxs, phosphines, and N-heterocyclic carbenes (NHC), bound to a transition metal center usually afiects the selectivities and reaction rates in the organic reactions. Styring et al. described the preparation of a Pd (Il)-salen complex immobilized on Merrifield resin (42). The polymer catalyst facilitated the Suzuki-Miyaura cross-coupling reaction in a continuous-flow system (Scheme 7.32) [130]. The reactor continuously afforded biaryl adducts (43) from aryl... 

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