Suzuki-Miyaura coupling side reactions

Under the reaction conditions, phenylacetylene was found to be a much more reactive coupling partner than arylboronic acids in the analogous Suzuki-Miyaura coupling, as in addition to the desired product (38), alkynylation and further addition reactions occurred with a variety of transient palladium(II) species (Scheme 27). Despite these undesired side reactions, Catellani was able to fine-tune the reaction conditions to form predominantly product 38 or 39. The formation of the desired product 38 (and suppression of product 39) is promoted by acceleration of norbomene carbopalladation by KOAc [47] and by using an excess of alkyl halide affording several structurally similar unsymmetrical alkyne products in good yields (Scheme 28). 

Another example of a similar palladium migration process was reported by Buchwald as a side reaction in the Suzuki-Miyaura coupling of 2,4,6-tri-tert-butylbromobenzene (Scheme 8) [64], Contrary to expectations, Suzuki-Miyaura... 

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