Applications of Hexyleneglycol Alkenylboronic Esters

1 VinylBhg in Heck Reactions from Higher Alkenylboronic 

P-Substituted vinylboronic esters were isolated in fair to high yields from the coupling under classical Heck conditions of vinylBhg with (hetero)aryl iodides and bromides (Table 3.1, entries 1-3). A dienyl boronic ester was obtained by coupling of vinylBhg with a vinyl iodide derived from phenylgly-cine (entry 4). The preparation of a styryl boronic ester with a sulfonamide moiety is described in a patent (entry 5) this product was later used in a Suzuki-Miyaura reaction.  

During the development of the Heck reaction of vinylBhg, silver(i) (or thal-lium(i)) acetate was shown to be a useful stoichiometric additive for enhancing the selectivity in favor of the Heck-product, especially when the coupling partner is an alkenyl system. In the latter case, further improvement can be found in replacing triphenylphosphine with tri(o-tolyl)phosphine and using silver(i) acetate as the sole base.  

2 Suzuki-Miyaura Couplings with Hexylene-glycol Alkenylboronic Esters 

On the other hand, vinylBhg was disearded for the 100 g seale synthesis of the latex monomer HESS (4-hydroxyethylsulfonylstyrene, Seheme 3.22), because the Suzuki-Miyaura reaction with the aryl bromide was found to be capricious. Commercial potassium vinyltrifluoroborate was ultimately chosen despite the added cost. 

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