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Cross-Couplings in Water
Conducting transition metal-catalyzed cross-coupling chemistry in water
instead of organic solvent has a number of potential benefi ts in terms of
cost, environmental impact, safety, and impurity profi les. Increasing focus
on the “green-ness” of chemical processes has further promoted recent
developments in this fi eld. The actual means of implementing reactions
in water, however, especially at room temperature and for water-insoluble
organic substrates, has not always been clear. One solution that has
been applied to a broad range of transition metal-catalyzed processes is
the use of small amounts of a nanomicelle-forming amphiphile in water,
which provides a lipophilic medium in which cross-coupling reactions
can take place.
Micellar Catalysis
Aldrich.com
Synthetic Reagents
Troy Ryba, Ph.D.
Product Manager
troy.ryba@sial.com
TPGS–750–M: Second Generation Amphiphile for Organometallic Chemistry in Water @ RT
Beginning in 2008, Lipshutz et al. published a series of papers demonstrating
the viability of surfactant promoted, transition metal-catalyzed
chemistry in water at room temperature. Using a variety of commercially
available surfactants, a number of palladium- and ruthenium-catalyzed
processes were found to be amenable to mild, room temperature reactions
in water. Products can be recovered from the aqueous phase using
standard extraction procedures and in high isolated yields.
TPGS–750–M: A Second Generation
Amphiphile
TO ORDER: Contact your local Sigma-Aldrich offi ce (see back cover), or visit Aldrich.com/chemicalsynthesis.
Lipshutz and co-workers have recently developed a second
generation technology to their original PTS-enabling surfactant based
on a polyoxyethanyl-α-tocopheryl succinate derivative, TPGS-750-M
(733857) (Figure 1). This designer surfactant is composed of a lipophilic
α-tocopherol moiety and a hydrophilic PEG-750-M chain, joined by an
inexpensive succinic acid linker, and spontaneously forms micelles upon
dissolution in water. The balance and composition of TPGS-750-M’s
lipophilic and hydrophilic components has been tailored to promote a
broader array of chemistry in water more effi ciently than that seen in PTS.
Furthermore, this new, more practical surfactant can be readily substituted
for older amphiphiles, usually with equal or greater
effi ciency in terms of both yield and reaction times.
Figure 1: TPGS–750–M.
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*Special thanks to Professor Bruce Lipshutz, Zarko V. Boskovic and Alex R. Abela of
University of California, Santa Barbara for contributing this article on TPGS-750-M.