Designer Surfactant For Organocatalysis

A micelle-forming molecule that functions as a solvent, surfactant, and organocatalyst rolled into one provides a “green” platform for carrying out organic reactions in water, according to Bruce H. Lipshutz and Subir Ghorai of the University of California, Santa Barbara, who created the catalytic amphiphile (Org. Lett., DOI: 10.1021/ol203242r). In 2009, Lipshutz and Ghorai first reported polyoxyethanyl ubiquinyl sebacate, or PQS, a molecule derived from the dietary supplement coenzyme Q₁₀ that features a hydroquinone ring with lipophilic polyprenoid and hydrophilic polyethylene glycol side chains. In water, PQS forms nanoscale micelles, which are ideal nanoreactors for organic synthesis. Lipshutz and Ghorai initially attached a ruthenium carbene catalyst to the PQS ring and tested the micellar system by carrying out olefin metathesis reactions. They have now created a metal-free version by attaching proline to the PQS ring and tested it by carrying out aldol reactions in water at room temperature. “The main issue with organocatalysis is that a large amount of catalyst is typically needed, and ultimately most of it is lost during product isolation,” Lipshutz says. “The PQS system solves this problem by allowing the nanomicelles to be recycled in the flask without loss of the catalyst.”