1,4-Diphosphorinane\nSynthesis at a Cationic Aluminum(III)\nCenter

Lewis acidic group 13 cations are\nuseful mediators of\nsmall-molecule\nand catalytic reactivity alike. Previous work has elaborated on the\nuse of bulky β-diketiminate Al(III) cations for the cycloaddition\nand intermolecular coupling of alkene substrates, giving new [Al]–C\nbonds. Motivated by a desire to prepare aluminum/phosphorus-containing\nambiphilic ligands, here we probe the intramolecular reactivity of\nmono- and diphosphines bearing a pendent alkene group. Despite the\ndrive for Al–P bond formation (as shown by control experiments),\nreaction of a specialized allyl-appended diphosphine results in rapid\ncyclization, producing an aluminum-bound 1,4-diphosphorinane (six-membered\nring). Together, this contribution offers a complementary route toward\nthis class of molecule and emphasizes the importance of substrate\ndesign characteristics such as phosphorus/alkene(β-carbon) linker\nlength to accessing productive cyclization. The subsequent reactivity\nof this heterocycle, including coordination chemistry with gold(I),\nare additionally shared.