1,4-Diphosphorinane Synthesis at a Cationic Aluminum(III) Center

Lewis acidic group 13 cations are useful mediators of small-molecule and catalytic reactivity alike. Previous work has elaborated on the use of bulky β-diketiminate Al(III) cations for the cycloaddition and intermolecular coupling of alkene substrates, giving new [Al]–C bonds. Motivated by a desire to prepare aluminum/phosphorus-containing ambiphilic ligands, here we probe the intramolecular reactivity of mono- and diphosphines bearing a pendent alkene group. Despite the drive for Al–P bond formation (as shown by control experiments), reaction of a specialized allyl-appended diphosphine results in rapid cyclization, producing an aluminum-bound 1,4-diphosphorinane (six-membered ring). Together, this contribution offers a complementary route toward this class of molecule and emphasizes the importance of substrate design characteristics such as phosphorus/alkene(β-carbon) linker length to accessing productive cyclization. The subsequent reactivity of this heterocycle, including coordination chemistry with gold(I), are additionally shared.