2,6-Bis(trifluoromethyl)phenylboronic Esters as Protective Groups for Diols: A Protection/Deprotection Protocol for Use under Mild Conditions

The application of 2,6-bis­(trifluoromethyl)­phenyl boronic acid (<i>o</i>-FXylB­(OH)<sub>2</sub>; <i>o</i>-FXyl = 2,6-(CF<sub>3</sub>)<sub>2</sub>C<sub>6</sub>H<sub>3</sub>) as a recoverable and reusable protective agent for diols is described. The resulting cyclic boronic esters are water- and air-stable and tolerant to various organic transformations. Moreover, they can be deprotected under mild conditions. This methodology was applied to the synthesis of a highly conjugated enetriyne natural product with anti-angiogenic activities.