Transition-Metal-Free Hydrosulfonylation of 1,3-Dienes with Sulfinic Acids: Efficient Approach to Branched Allylic Sulfones

Abstract

Branched allylic sulfones are privileged scaffolds widely distributed in bioactive molecules, and organic functional materials. Some methods for the synthesis of allyl sulfones have been developed, such as Tsuji-Prost reaction, hydrosulfonylation and radical addition reactions. Despite these advances, the transition-metal-free hydrosulfonylation of unactive 1,3-diene leading to branched allylic sulfones has rarely explored. Herein, a boron-catalysed highly regioselective hydrosulfonylation of 1,3-diene with sulfinic acid has been explored to construct a broad scope of branched allylic sulfones. The reactions proceed smoothly without the help of transition-metal-catalyst. Abundant structural motifs have also been obtained through simple transformation from the generated allylic sulfone products. Compared with the previous methods, this protocol exhibited advantages as following: 1) readily available starting material without pre-treatment; 2) under the catalysis of inexpensive boron trifluoride etherate, avoidance of transition-metal-catalyst; 3) simple operation and easy scale-up, and does not require dry conditions, an inert atmosphere or a water scavenger; 4) excellent atom economy and regioselectivity.