Palladium-CatalyzedSite-Selective RegiodivergentCarbocyclization of Di- and Trienallenes: A Switch between SubstitutedCyclohexene and Cyclobutene

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 <i>cis</i>-1,4-disubstituted cyclohexenes and <i>trans</i>-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 <i>cis</i>-1,4-disubstituted cyclohexenes and fully substituted <i>trans</i>-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.