Efficient Synthesis of Aryl Vinyl Ethers Exploiting 2,4,6-Trivinylcyclotriboroxane as a Vinylboronic Acid Equivalent

The synthesis of functionalized aryl vinyl ether derivatives can be readily achieved utilizing a room-temperature copper(II) acetate mediated coupling of substituted phenols with 2,4,6-trivinylcyclotriboroxane−pyridine complex in the presence of a suitable base. The scope of the procedure was
demonstrated by the generation of an array of substituted aryl vinyl ethers. The reaction was seen
to be tolerant of a diverse range of functional groups yielding products in high isolated yields. We
have shown that one role of an amine base in the reaction sequence is the in situ generation of an
amine coordinated boroxine ring. An X-ray crystal structure and low temperature 11B NMR study
of 2,4,6-trivinylcyclotriboroxane−pyridine complex demonstrated the nature of the tetracoordinate
boron species, which may have a key role to play within the reaction sequence.