In recent years,boronic acids have gained significant importance in organic synthesis.The synthetic applications of these compounds include the Suzuki-Miyaura cross-coupling reaction,the rhodium-catalyzed addition onto aldehydes~2 and alkenes,the copper diacetate-promoted cross-coupling reactions involving amines,alcohols,and thiols,as well as the borono-Mannich reaction.Both aryl- and alkenylboronic acids can participate in these reactions;however,the challenge posed by the isolation of alkenylboronic acids has significantly hampered their use.Indeed,most alkenylboronic acids are unstable under conventional purification conditions and their corresponding esters,although stable,are not suitable for some synthetic applications.As part of our ongoing program on the applications of unsaturated boronic acids in organic synthesis,we became interested in developing a convenient and general procedure for the preparation and isolation of free alkenylboronic acids that could complement our solid-phase capture approach.
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