Alkoxide Base-Mediated Methyl Boration of Aryl Alkenes and Arylidenecyclopropanes.

A transition-metal-free methyl boration of aryl alkenes with B2pin2 and methyl iodide has been achieved using the alkoxide base tBuOK as the sole mediator. In contrast, previous alkene methyl borations employ transition-metal catalysts. Apart from styrenes, arylidenecyclopropanes have also been found to undergo efficient transformations with the retention of the cyclopropyl rings for the synthesis of tertiary boronates. Mechanistic investigations revealed the involvement of an anionic intermediate in the reaction process.