Subir Ghorai

Rate Enhanced Olefin Cross-Metathesis Reactions: The Copper Iodide Effect

Copper iodide has been shown to be an effective cocatalyst for the olefin cross-metathesis reaction. In particular, it has both a catalyst stabilizing effect due to iodide ion, as well as copper(I)-based phosphine-scavenging properties that apply to use of the Grubbs-2 catalyst. A variety of Michael acceptors and olefinic partners can be cross-coupled under mild conditions in refluxing diethyl ether that avoid chlorinated solvents. This effect has also been applied to chemistry in water at room temperature using the new surfactant TPGS-750-M.

Manipulating Micellar Environments for Enhancing Transition Metal-Catalyzed Cross-Couplings in Water at Room Temperature

The remarkable effects of added salts on the properties of aqueous micelles derived from the amphiphile PTS are described. Most notably, Heck reactions run in the presence of NaCl lead to couplings on aryl bromides in water at room temperature. Olefin cross- and ring-closing metathesis reactions run in the presence of small amounts of pH-lowering KHSO(4) are also accelerated, another phenomenon that does not apply to typical processes in organic media. These salt effects allow, in general, for synthetically valuable C-C bond-forming processes to be conducted under environmentally benign conditions. Recycling of the surfactant is also demonstrated.

Gold‐Catalyzed Cyclizations of cis‐Enediynes: Insights into the Nature of Gold–Aryne Interactions

Golden aryne? Gold aryne complexes are inferred as transition states in dual gold-catalyzed cyclizations of cis-enediynes (see scheme; DCE = 1,2-dichloroethane). They are better described as ortho-aurophenyl cations, which react with weak nucleophiles and undergo facile intramolecular insertions into C(sp(3))-H bonds. Indanes, fused heteroarenes, and phenol derivatives are readily prepared using this method.

Organocatalysis in Water at Room Temperature with In-Flask Catalyst Recycling

A new designer surfactant is described containing a covalently bound organocatalyst, proline. This species is water-soluble and, via spontaneous nanomicelle formation, catalyzes aldol reactions on water-soluble or -insoluble substrates in water as the only medium. Recycling the catalyst is trivial, as the amphiphile/catalyst remains in the aqueous phase in the flask.

Modified Routes to the “Designer” Surfactant PQS

Described herein are newly developed, straightforward entries to polyethyleneglycol ubiquinol succinate (PQS, n = 2), a designer surfactant that serves as precursor to micelle-forming, covalently bound catalysts for a variety of transformations in water with in-flask catalyst recycling.

Deprotection of Homoallyl (hAllyl) Derivatives of Phenols, Alcohols, Acids, and Amines

The homoallyl moiety, (h)Allyl, is presented as a general protecting group for several functionalities. It can be chemoselectively removed via a sequential, one-pot cross-metathesis/elimination sequence.

The Hydrophobic Effect Applied to Organic Synthesis: Recent Synthetic Chemistry “in Water”

Recent developments over the past few years in aqueous micellar catalysis are discussed. Applications to problems in synthesis are highlighted, enabled by the use of surfactants that self-aggregate in water into micelles as nanoreactors. These include amphiphiles that have been available for some time, as well as those that have been newly designed. Reactions catalyzed by transition metals, including Pd, Cu, Rh, and Au, are of particular focus.