New Horizon in Phospha-Michael Reaction: Ultrafast Double Addition of P-H Bond-Bearing Nucleophiles to Electron-Deficient Triple Bonds and Its Use for Functional Monomer Synthesis and Polymer Modification

In this work, a novel, straightforward, robust, fast,and organocatalyst-mediatedphospha-Michael reaction (OCPMR) was developed for the addition ofphosphorus nucleophiles to electron-deficient alkynes. Several P-Hbond-bearing compounds with either fully aliphatic or aromatic unitswere utilized for this newly developed reaction, and it was foundthat phosphorous species containing only aromatic groups reacted withactivated alkynes within 5 min at room temperature. The reaction ledto a fast double-addition of the phosphorous compounds to the triplebond of the alkynes. An in-depth analysis of the reaction mechanismand selectivity of this OCPMR was performed using computational methods.Using the developed method, double-phosphorylated allyl-functionalmonomers were synthesized and subsequently used for the synthesisof linear and crosslinked polymers via thiol-ene photopolymerization.The thermoset materials exhibited LOI values as high as 26.4%. Wealso showed that polyesters having electron-deficient triple bondscould be easily functionalized with the P-H bond-bearing compounds.The synthetic method proposed herein promises easy and fast P-Cbond formation under mild reaction conditions, and it is a straightforwardmethod for the synthesis of phosphorus-containing monomers, linearor crosslinked polymers, and for polymer post-functionalization. Webelieve this feature will be of great interest not only to materialchemists and polymer scientists but also to organic chemists, pharmaceuticalresearchers, etc.