Palladium and copper catalyzed synthesis of allyl- and allenylboronic acids was developed using diboronic acid (tetrahydroxy diboron) as boron source. Allylboronic acids are unprotected analogues of allylboronates (such as allyl-Bpin), which proved to be excellent reagents in selective allylation of carbonyl compounds. Because of the lack of protection of the boron functionality allylboronic acids are more oxygen sensitive than their allylboronate counterparts. On the other hand, isolated allylboronic acids have a much broader synthetic scope than allyl boronates. For example, allylboronic acids have a higher reactivity in allylation of carbonyl compounds and imines as well as in cross-coupling reactions. In addition, the in situ esterification of allylboronic acids is much easier than for allylboronates (allyl-Bpin and analogues). This property can be employed in asymmetric allylation using BINOLs as catalysts. Similar applications for asymmetric propargylboration will also be presented.

Free the boronic acids! Allyl- and allenylboronic acids in organic synthesis

255th National Meeting (2018)

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