Enantioselective Trifunctionalization of Terminal Alkynes
Langxuan Yang, M. Cole Detels, Gojko Lalić
Abstract
The stereoselective synthesis of alkenes has been one of the central objectives in organic chemistry. Significant advances in synthetic methodology have made mono- and disubstituted alkenes widely accessible from a variety of readily available precursors. However, increased steric hindrance in more highly substituted alkenes limits the effectiveness of these methods, and as a result, the efficient and selective synthesis of highly substituted alkenes remains a formidable challenge. Here, we demonstrate palladium-catalyzed trifunctionalization of terminal alkynes using organoboranes and allylic carbonates as coupling partners. This transformation provides tetrasubstituted alkenes with excellent regioselectivity and diastereoselectivity. Moreover, regiodivergent, diastereo- and enantioselective incorporation of the allylic fragment provides access to a wide range of complex 1,4-diene products. We present evidence that the palladium catalyst controls the selectivity of tetrasubstituted alkene formation and the selectivity of allylic substitution.