Microelectrode Array

September 3, 2007

Electrochemistry and Umpolung Reactions: New Tools for Solving Synthetic Challenges of Structure and Location

Feili Tang, Ceng Chen, Kevin D. Moeller
Synthesis 2007, 3411-3420

Electrochemistry is a powerful tool for initiating new umpolung reactions. In this paper, two examples are provided. One demonstrates the use of electrochemistry for reversing the polarity of known functional groups and triggering carbon-carbon bond formation. The second demonstrates the use of electrochemistry for reversing the polarity of a chemical reagent, a technique that allows for spatially locating synthetic transformations on addressable chips.

 

November 24, 2006

Building Addressable Libraries: The Use of a Mass Spectrometry Cleavable Linker for Monitoring Reactions on a Microelectrode Array

Ceng Chen, Gabriella Nagy, Amy V. Walker, Karl Maurer, Andy McShea, and Kevin D. Moeller
J. Am. Chem. Soc., 2006, 128 (50), 16020–16021

Time-of-flight secondary ion mass spectrometry (TOF SIMS) has been used in conjunction with a mass spectrometry cleavable linker to determine the percent conversion of reactions that were conducted site-selectively on an addressable microelectrode array. When combined with fluorescence techniques for analysis of the reactions, the TOF SIMS experiment provides a means for optimization of both reaction confinement and reaction efficiency on the microelectrode arrays.

 

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.

 

January 28, 2006

Building Addressable Libraries: Site Selective Coumarin Synthesis and the “Real-Time” Signaling of Antibody−Coumarin Binding

Eden Tesfu, Kris Roth, Karl Maurer, and Kevin D. Moeller
Org. Lett., 2006, 8 (4), 709–712

The feasibility of using active semiconductor chips containing addressable arrays of microelectrodes for the “real-time” monitoring of biologically relevant binding events has been demonstrated by detecting the binding of a coumarin substrate by an anticoumarin antibody. The coumarin substrate was synthesized proximal to predetermined electrodes on the chip with the use of a Pd(II) reagent that was itself generated by using the selected electrodes. Once the coumarin was synthesized, its binding to the anticoumarin antibody was detected by monitoring the current associated with a ferrocene−ferrocinium ion redox cycle that was established between the electrodes on the chip and a remote auxiliary electrode.

 

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.
 
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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