Palladium-Catalyzed Synthesis of Alkylidenecyclobutanes
Stereoselective Access to Alkylidenecyclobutanes through γ-Selective Cross-Coupling Strategies.
Org. Lett. 2017;
18 September 2017 (online)
Alkylidenecyclobutanes are useful strained building blocks that can also be found in a number of natural compounds. In this work, the authors disclose the use of a γ-selective Suzuki–Miyaura cross-coupling for the synthesis of this class of compounds containing a quaternary stereocenter.
Achiral cyclobutenylmethylboronic esters reacted with aryl halides in the presence of a palladium catalyst and potassium hydroxide. The corresponding products were obtained in moderate to excellent yields and essentially with perfect γ-selectivity. In the case of δ-substituted substrates, high levels of diastereoselectivity were obtained. The use of (chiral) α-substituted starting materials generated the corresponding products containing a trisubstituted double bond functionality in high stereoselectivity (and enantioselectivity).