Catalytic Transfer Reactions of Nonstabilized Carbenes

Carbenes are versatile reactive intermediates that display orthogonal reactivity to common nucleophilic and electrophilic functional groups. Catalytic carbene transfer reactions were first discovered over a half century ago, and numerous examples of [n + 1]-cycloaddition reactions have since been developed, often with control over diastereo- and enanatioselectivity. Most of these reactions rely on the controlled decomposition of diazoalkanes as a central strategy to access reactive carbene equivalents.

 

Despite the utility of diazoalkanes in organic synthesis, they are inherently limited by the need for stabilizing substituents such as aryl or carbonyl groups. In order to develop transfer reactions of nonstabilized carbenes, it is necessary to consider an alternative set of precursors. Our group has shown that nickel and cobalt catalysts can promote reductive [n + 1]-cycloaddition reactions using readily available and indefinitely stable 1,1-dichloroalkanes and 1,1-dichloroalkenes as precusors for carbenes and vinylidenes, respectively. In this seminar, I will describe our development of new cycloaddition methods and our current hypotheses about the mechanisms of these reactions.