Organophosphine as an Alkyl Transfer Shuttle for the Direct β-Alkylation of Chalcones Using Alkyl Halides.

We report an efficient alkyl transfer strategy for the direct β-alkylation of chalcones using commercially available alkyl bromides as alkyl reagents. In this transformation, the ortho -phosphanyl substituent in the chalcones is crucial for controlling their reactivity and selectivity. It also serves as a reliable alkyl transfer shuttle to transform electrophilic alkyl bromides into nucleophilic alkyl species in the form of quaternary phosphonium salts and transfer the alkyl group effectively to the β-position of the chalcones. This alkyl transfer strategy can be further extended to the alkenylation of ortho -phosphanyl benzaldehydes to assemble functionalized polyenes.