Convenient Preparation of Cycloalkenyl Boronic Acid Pinacol Esters

Abstract

A practical method for the preparation of cycloalkenyl boronic acid pinacol esters is described. These important synthetic intermediates are typically made using more expensive methods like transition metal-catalyzed borylation of alkenyl halides or triflates. In this work, they are obtained from the simple corresponding cycloalkanones, which are subjected to Shapiro reaction conditions followed by trapping with a borate ester. The requisite products are obtained in very good to excellent yields, and the reactions can be scaled up to multigram amounts. By providing a simple alternative to common methods that make use of expensive transition-metal catalysts and formation of sensitive intermediates, this convenient method will be useful for the synthesis of ring-containing partners for Suzuki–Miyaura cross-coupling and other reactions employing boronic esters as substrates.

Keywords:

• Boronic acid
• boronic esters
• Shapiro reaction
• Suzuki–Miyaura cross-coupling

ACKNOWLEDGMENTS

The Spectral Services at the University of Alberta are thanked. V. R. acknowledges the Alberta Ingenuity Foundation for a Studentship. Financial support for this research was provided by the Natural Sciences and Engineering Research Council of Canada.