Phosphinidenes [R−P] are regarded as valuable and simple P₁ building blocks for synthesizing organophosphorus compounds and as diverse ligands in transition-metal complexes. Owing to the scarcity of isolable examples¹, alternative precursors known as phosphinidenoids have been developed to facilitate phosphinidene transfer reactions. However, these methods are often limited in terms of substituents R, significantly restricting the synthetic potential of phosphinidenes as P₁ building blocks.²

In response to this limitation, we have designed a phosphinidene bearing a suitable leaving group that allows functionalization by various nucleophiles following phosphinidene transfer.³ Cationic imidazoliumyl-phosphinidene [L_C−P]⁺ can readily be transferred from phosphonio-phosphanides I, for example, to a range of thioketones, producing cationic phosphaalkenes II. Subsequent treatment of these compounds with nucleophiles, such as Grignard reagents, results in the replacement of the imidazoliumyl substituent, enabling easy access to both known and unprecedented phosphaalkenes III. We will discuss the scope and mechanism of this innovative synthetic approach.

Acknowledgements: We gratefully acknowledge financial support from the Deutsche Forschungsgemeinschaft (DFG grant numbers WE4621/6-1) and the Fonds der Chemischen Industrie (Kekulé Fellowship for P.R.).

References:

[1] Liu, L.; Ruiz, D. A.; Munz, D.; Bertrand, G. A Chem 2016, 1, 147−153.

[2] see e.g.: Transue, W. J.; Velian, A.; Nava, M.; García-Iriepa, C.; Temprado, M.; Cummins, C. C. J. Am. Chem. Soc. 2017, 139, 10822−10831; Shah, S.; Protasiewicz, J. D. Chem. Commun. 1998, 1585−1586.

[3] Royla, P.; Schwedtmann, K.; Zeyu, H., Fidelius, J.; Gates, D. P., Gomila, R. M., Frontera, A., Weigand, J. J. J. Am. Chem. Soc. 2023, 145(18), 10364−10375, https://doi.org/10.1021/jacs.3c02256.