Synthesis of allenyl-B(MIDA) via hydrazination/fragmentation reaction of B(MIDA)-propargylic alcohol

Allenylboronates represent a very intriguing class of organoborons but are challenging to synthesis. In addition, these compounds are typically unstable, rendering the separation difficult. We report herein a practical and concise route to a new class of stable, easy-separable allenyl B(MIDA) via a hydrazination/fragmentation of B(MIDA)-propargylic alcohols. The synthesis of optically active allenyl B(MIDA) was also achieved. Interesting reactivity of the resulting product was observed.