Diarylmethane-phosphonium salts: Synthesis and new transformations

Organo-phosphorous compounds have emerged as highly versatile and useful building blocks in organic chemistry. These compounds exhibit numerous forms such as alkylated or arylated phosphines, phosphonium salts, phosphonic and phosphinic acids, which can be applied as reagents, catalysts, chiral ligands, and ionic liquids in a wide range of chemical processes. In particular, organophosphorus-based Wittig-salts, which are ranked among the most powerful compounds for C-C bonds construction, and are commonly used in olefination reactions.¹ Hence, it is of upmost importance to further develop such phosphonium salt-based transformations, which may provide new opportunities and facilitate the implementation of novel synthetic strategies. In this work, we will demonstrate a facile, mild, and efficient approach for the synthesis of diarylmethane-phosphonium salts in high atom economy and their unique applications in organic synthesis. Under our developing methodology, a variety of diarylmethane-phosphonium-salts have been synthesized. The reactions delivered high levels of chemoselectivity and produced only a single regioisomer. We envision that these diarylmethane-phosphonium salts hold a great promise for providing a unified approach for various synthetic transformations such as the preparation of: (1)- tetra-arylethanes via homo-coupling, (2)- diarylmethane through reduction, and (3)- ketones by activation with oxygen. Additionally, the outcome of this work can be extended in the future towards the synthesis of enantiopure-organoboryl compounds, tetraarylethanes, and the use of the diarylphosphonium-salts as catalysts in different organic transformations. Moreover, these transformations have the potential to be applied for the late-stages diversification/ functionalization of various kinds of bioactive molecules.

1. Oleg I. Kolodiazhnyi, (1999) Phosphorus Ylides: chemistry and application in organic synthesis, New York; Chichester ; Brisbane ; Singapore ; Toronto : Wiley-VCH, 1999.