Palladium-Catalyzed Site-Selective Regiodivergent Carbocyclization of Di- and Trienallenes: A Switch between Substituted Cyclohexene and Cyclobutene

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High Resolution Image Download MS PowerPoint Slide Nature efficiently produces a myriad of structurally diverse carbon ring frameworks from common linear precursors via cyclization reactions at specific olefinic sites in dienes or polyenes. In contrast, achieving the site-selective functionalization of diene or polyene substrates remains a formidable challenge in chemical synthesis. Herein, we report a pair of highly site-selective, regiodivergent carbocyclization reactions of dienallenes and trienallenes, enabling the efficient synthesis of cis -1,4-disubstituted cyclohexenes and trans -1,2-disubstituted cyclobutenes from a common precursor with high diastereoselectivity. Remarkably, simple achiral organophosphoric acids and amines are identified as powerful ligands for controlling these palladium-catalyzed regiodivergent carbocyclizations. This approach represents the first example of site-selective regiodivergent carbocyclization, providing a practical method for the stereospecific synthesis of thermodynamically disfavored cis -1,4-disubstituted cyclohexenes and fully substituted trans -1,2-cyclobutenes. Additionally, the methodology developed offers general insights into the development of metal-catalyzed site-selective, regiodivergent carbocyclizations of diene and polyene precursors, mimicking natural carbocyclization processes.