Triphenylphosphine resin

Coupling reactions to make esters and amides are among the most widely used organic transformations. We report efficient procedures for amide bond formation and for the monoesterification of symmetrical diols in excellent yields without any requirement for high dilution or slow addition using resin-bound triarylphosphonium iodide. Easy purification, low moisture sensitivity, and good to excellent yields of the products are the major advantages of this protocol.

Described herein is a comparative study of immobilised triphenylphosphine (PS-PPh3 ) and 1-hydroxybenzotriazole (PS-HOBt) to mediate amide couplings under continuous flow. Compared to Appel-type amidations (PS-PPh3 ), the developed 'catch-and-release' approach (PS-HOBt) afforded near-quantitative amide conversions. Utilising this strategy, sulfonyl chloride amenability enabled facile access to an expanded library of sulfonate and sulfonamides. Post-constructional peptide modification was also demonstrated, affording two Nβ -functionalised pentapeptides in high yields and purities. In contrast to frequently utilised coupling agents, the PS-HOBt resin could be recycled six times without a reduction in efficacy or regeneration requirements.

Heterogeneous polymer-supported triphenylphosphine oxides based on the rasta resin architecture have been synthesized, and applied as reagent precursors in a wide range of halogenation reactions. The rasta resin-triphenylphosphine oxides were reacted with either oxalyl chloride or oxalyl bromide to form the corresponding halophosphonium salts, and these in turn were reacted with alcohols, aldehydes, aziridines and epoxides to form halogenated products in high yields after simple purification. The polymer-supported triphenylphosphine oxides formed as a byproduct during these reactions could be recovered and reused numerous times with no appreciable decrease in reactivity.