2.4.6- Trivinylcyclotriboroxane-pyridine complex

Suzuki-Miyaura cross-coupling of 343 with 2,4,6-trivinylcyclotriboroxane-pyridine complex proved to be a very efficient method for the generation of the styrenes 337, R2 = Boc in high yields (Scheme 104)188. The procedure was tolerant to all the aryl substituents attempted and to the three different nitrogen substituents. 

Furthermore, [Pd(Triphos)](CF3 803)2 has been used as an effective catalyst for the addition of amine to alkyne, and the vinyl carbamate derivatives can be prepared in one step from acetylene, CO2, and one of the following amines dialkylamine, morpholine, piperidine, and pyrrolidine, using RuCl3 3H20 or [RuCl2(norbornadiene)]n as the catalyst. In addition, the preparation of vinyl phenyl ethers has been modified using tributyl(vinyl)tin or 2,4,6-trivinylcyclotriboroxane-pyridine complex as the vinyl source. 

Alkenylboron derivatives are readily available by stereo-defined hydroboration of alkynes and used for the preparation of styrene derivatives by alkenyl-aryl coupling. Vinylboronic acid (81), the most simple alkenylboronic acid, is difficult to handle, because it undergoes uncontrollable polymerization. Its anhydride, 2,4,6-trivinylcyclotriboroxane (82)-pyridine complex, is stable, and can be used conveniently for the coupling. Vinylation of 2-bromoanisole with 82 proceeds in refluxing DME using K2CO3 as a base fo provide 2-vinylanisole (83) [80]. 

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