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Experimental procedures have been developed to provide at the laboratory scale an efficient and relatively inexpensive continuous flow processing system to undertake metathesis chemistry. Glass discs, coated with porous silica particles impregnated with Grubbs (I) generation or Hoveyda-Grubbs (II) generation catalysts through non-covalent interactions, have been successfully used as annular zones for in situ metathesis reactions. The supported catalysts were active for ring closing metathesis and self-metathesis reactions with a variety of substrates with nearly quantitative conversion depending on the substrate structure. Advantages of these procedures include the ability to conduct reactions efficiently at small (low mmole) scale under ambient laboratory conditions, thereby avoiding the need for high energy/thermal procedures. Multiple experiments can be undertaken during the same day if catalyst screening is required. Moreover, separation of starting materials from products can be achieved using the same unit operations, avoiding the need for additional purification steps, thereby reducing the total solvent consumption.

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Synthetic procedures, based on integrated flow chemical methods, have been developed for the sequential chemo-selective Suzuki-Miyaura cross-coupling of 1,4-dibromo-2-nitrobenzene (1) with various arylboronic acids. The first Suzuki coupling step used a phosphine-(ligand)-free palladium catalyst at room temperature and gave regio-selective coupling of (1) at the orthoposition to the nitro group. The bromo-biaryl product was then directly subjected in situ to a second coupling step, using different arylboronic acids, as a continuous in-flow operation. Based on this methodology, a number of unsymmetrically substituted p-terphenyl compounds were synthesized in excellent overall yields. This approach provides a convenient route to this class of compounds, and is suited for the generation of targeted chemical libraries, or the synthesis of precursors of biologically active natural product analogues that contain the p-terphenyl core. During the first coupling step, dimerization at low levels of the bromo-biaryl intermediate occurred, leading to formation of quaterphenyl compounds.