Transition Metal

February 24, 2009

Building Addressable Libraries: Site-Selective Suzuki Reactions on Microelectrode Arrays

Libo Hu, Karl Maurer and Kevin D. Moeller

Org. Lett., 2009, 11 (6), pp 1273–1276

A site-selective Suzuki reaction has been developed for use on microelectrode arrays. The reaction conditions employed are similar to those used to achieve site-selective Heck reactions. The reaction can be run with either an aryliodide attached to the surface of the array and an arylboronic acid in solution or with an arylboronic acid attached to the surface of the array and an arylbromide in solution. Both allyl acetate and air are effective confining agents for the reaction. The reactions are compatible with arrays containing either 1024 microelectrodes cm-2 or 12,544 microelectrodes cm-2.

 

July 3, 2006

Building Addressable Libraries: The Use of Electrochemistry for Spatially Isolating a Heck Reaction on a Chip

Jun Tian, Karl Maurer, Eden Tesfu, and Kevin D. Moeller
J. Am. Chem. Soc., 2005, 127 (5), 1392–1393

Pd(0) was generated at preselected sites on an electrochemically addressable chip and then utilized to effect a Heck reaction. The Pd(0) was confined to the preselected electrodes with the use of allylmethyl carbonate. Unlike most mediated electrochemical reactions, the electrolysis in this case was not used to convert a stoichiometric process into a catalytic one by recycling the metal. Instead, the unique environment of the chip was used to interfere with a catalytic process to make it stoichiometric. This was done to gain spatial control over the reaction. The development of a strategy for conducting Pd(0)-catalyzed reactions on the chips should greatly expand the synthetic chemistry available for building chip-based libraries.

 

December 13, 2005

Building Addressable Libraries: Spatially Isolated, Chip-Based Reductive Amination Reactions

Eden Tesfu, Karl Maurer, and Kevin D. Moeller

J. Am. Chem. Soc., 2006, 128 (1),  70–71

Pd(II) reagent has been generated at preselected sites on an electrochemically addressable chip and used to effect the oxidation of the neighboring alcohols on the polymer coating the chip’s surface. The resulting carbonyls were then used to accomplish site-selective reductive amination reactions on the chips. The work demonstrates that the confinement strategy developed for spatially isolated Wacker oxidations to specific sites on the chips is general and can be used for other Pd(II)-based reactions.
 
October 27, 2005

Electrochemically Assisted Heck Reactions

Jun Tian and Kevin D. Moeller
Org. Lett., 2005, 7 (24), pp 5381–5383

During efforts to develop chip-based Heck reaction chemistry, it was discovered that normal solution-phase Heck reactions can be dramatically accelerated using electrochemistry. The acceleration makes room temperature Heck reactions proceed at synthetically useful rates in the absence of added ligand. Presumably, the current passed through the reaction maintains a high level of active catalyst.

 

April 28, 2004

Building Addressable Libraries: The Use of Electrochemistry for Generating Reactive Pd(II) Reagents at Preselected Sites on a Chip

Eden Tesfu, Karl Maurer, Steven R. Ragsdale, and Kevin D. Moeller
J. Am. Chem. Soc., 2004, 126 (20), 6212–6213

A Pd(II) reagent has been generated at preselected sites on an electrochemically addressable chip. The reagent was used to effect the Wacker oxidation of an olefin substrate bound to the chip near the electrode. The use of ethyl vinyl ether in the solution above the chip effectively kept the Pd(II) reagent generated at the preselected electrode from migrating to neighboring electrodes and initiating Wacker oxidations at unwanted sites on the chip.

 

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