Substituted Cyclopropanols via Sequential Cyclopropanation and Oxidative Hydrolysis of Vinylboronates

We present a scalable, diastereoselective protocol for synthesizing cyclopropanols, including rare 2-substituted ones, via oxidative hydrolysis of cyclopropyl boron pinacolates. Our previous protocol for Pd-catalyzed cyclopropanation of vinyl boron pinacolates was adapted for flow conditions, allowing safe, scalable utilization of diazomethane and ensuring high yields of target products. The use of ethyldiazoacetate for cyclopropanation allows the formation of boronic acids in the first step; however, decreases the stability of cyclopropanols in the second, yielding esteraldehydes.