Benjamin R. Taft

Heck Couplings at Room Temperature in Nanometer Aqueous Micelles

A nonionic amphiphile such as Triton X-100 or the vitamin E-based PTS, both of which form nanomicelles in water, promotes Heck cross-couplings of non-water-soluble partners at ambient temperatures. These are the first examples of Heck reactions conducted in water (as the only solvent) at room temperature.

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.

Asymmetric Conjugate Reductions of Coumarins. A New Route to Tolterodine and Related Coumarin Derivatives

The combination of catalytic amounts of [(R)-DTBM-SEGPHOS]CuH in the presence of stoichiometric DEMS (diethoxymethylsilane) in toluene at room temperature leads to asymmetric reductions of 4-substituted coumarins. Several targets or their known precursors can be prepared in high yields and ees, including the muscarine receptor antagonist (R)-tolterodine.

New technologies in catalysis using base metals

Formation of C-C, C-N, and C-H bonds using three heterogeneous catalysts in the form of nickel-in-charcoal (Ni/C), nickel-on-graphite (Ni/Cg), and copper-in-charcoal (Cu/C) are described.

A Convenient Preparation of Di-p-chlorobenzyl Azodicarboxylate (DCAD)for Mitsunobu Couplings

Gram-scale synthesis of pure, bench-stable solid di- P-chlorobenzyl azodicarboxylate (DCAD)is performed in two steps WITHOUT resortingto chromatography. This novel reagent effects Mitsunobu couplingswith yields comparable to DEAD or DIAD, while addressing severalof the drawbacks frequently associated with these common reagents.