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Expanding Ligand Space: Preparation, Characterization, and Synthetic Applications of Air-Stable, Odorless Di-tert-alkylphosphine Surrogates

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posted on 24.04.2020, 11:42 by Thomas Barber, Stephen P. Argent, Liam T. Ball
The di-tert-alkylphosphino motif is common to many best-in-class ligands for late-transition-metal catalysis. However, the structural diversity of these privileged substructures is currently limited by the need to manipulate highly toxic, highly reactive reagents and intermediates in their synthesis. In response to this longstanding challenge, we report an umpolung strategy for the synthesis of structurally diverse di-tert-alkylphosphine building blocks via SN1 alkylation of in situ generated PH3 gas. We show that the productswhich are isolated as air-stable, odorless phosphonium saltscan be used directly in the preparation of key synthetic intermediates and ligand classes. The di-tert-alkylphosphino building blocks that are accessible using our methodology therefore enable facile expansion of extant ligand classes by modification of a previously invariant vector; we demonstrate that these modifications affect the steric and electronic properties of the ligands and can be used to tune their performance in catalysis.