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Phosphirenium Ions as Masked Phosphenium Catalysts: Mechanistic Evaluation and Application in Synthesis.

ABSTRACT: The utilization of phosphirenium ions is presented; optimized and broadened three-membered ring construction is described together with the use of these ions as efficient pre-catalysts for metal-free carbonyl reduction with silanes. Full characterization of the phosphirenium ions is presented, and initial experimental and computational mechanistic studies indicate that these act as a "masked phosphenium" source that is accessed via ring opening. Catalysis proceeds via associative transfer of {Ph₂P⁺} to a carbonyl nucleophile, H-SiR₃ bond addition over the C=O group, and associative displacement of the product by a further equivalent of the carbonyl substrate, which completes the catalytic cycle. A competing off-cycle process leading to vinyl phosphine formation is detailed for the hydrosilylation of benzophenone for which an inverse order in [silane] is observed. Experimentally, the formation of side products, including off-cycle vinyl phosphine, is favored by electron-donating substituents on the phosphirenium cation, while catalytic hydrosilylation is promoted by electron-withdrawing substituents. These observations are rationalized in parallel computational studies.

SUBMITTER: Gasperini D

PROVIDER: S-EPMC8495902 | biostudies-literature |

REPOSITORIES: biostudies-literature

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