March 22, 2010

Intramolecular Anodic Olefin Coupling Reactions: Using Competition Studies to Probe the Mechanism of Oxidative Cyclization Reactions

Hai-Chao Xu and Kevin D. Moeller

Org. Lett., 201012 (8), 1720–1723

A competition experiment was designed so that the relative rates of anodic cyclization reactions under various electrolysis conditions can be determined. Reactions with ketene dithioacetal and enol ether-based substrates that use lithium methoxide as a base were shown to proceed through radical cation intermediates that were trapped by a sulfonamide anion. Results for the oxidative coupling of a vinyl sulfide with a sulfonamide anion using the same conditions were consistent with the reaction proceeding through a nitrogen-radical.


October 29, 2009

A New Porous Reaction Layer for Developing Addressable Molecular Libraries

Libo Hu, Jennifer L. Bartels, Jeremy W. Bartels, Karl Maurer and Kevin D. Moeller

J. Am. Chem. Soc., 2009, 131(46), 16638–16639

A new diblock copolymer-derived porous reaction layer for microelectrode arrays has been tested for its stability and its compatibility with both site-selective synthesis and electrochemical signaling experiments. The diblock copolymer consisted of a cinnamoyl-substituted polymethacrylate block for attachment to the surface of the array and a bromo-substituted polystyrene block for selective functionalization of the surface proximal to microelectrodes in the array. Site-selective Suzuki, Heck, and Cu(I)-coupling reactions were all performed on the new reaction layer along with electrochemical impedance studies.


July 6, 2009

Building Addressable Libraries: Site-Selective Lewis-Acid (Sc(III)) Catalyzed Reactions

Bo Bi, Karl Maurer, and Kevin D. Moeller.
Angew. Chem. Int. Ed. Eng. 2009, 48, 5872

Lewis acid-catalyzed reactions have been site-selectively conducted on arrays having either 1024 microelectrodes cm-2 or 12,544 microelectrodes cm-2. The reactions employ Sc(III) generated at the microelectrodes as the Lewis acid, and confine the reagent to the electrodes utilized in its generation with the use of  2-phenylbenzthiazole  as a solution phase reductant. A multicomponent synthesis of a tetrahydropyran, a Diels-Alder reaction, and an esterification reaction were all shown to be compatible with the electrochemical generation of the Sc(III) and the confinement strategy.


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.


September 23, 2008

Intramolecular Anodic Olefin Coupling Reactions: The Use of a Nitrogen Trapping Group

Hai-Chao Xu and Kevin D. Moeller*

J. Am. Chem. Soc., 2008, 130 (41), pp 13542–13543

Anodic olefin coupling reactions using a tosylamine trapping group have been studied. The cyclizations are favored by the use of a less-polar radical cation and more basic reaction conditions. The most significant factor for obtaining good yields of cyclic product is the use of the more basic reaction conditions. The cyclizations allow for the rapid synthesis of substituted proline derivatives.


August 5, 2008

Microelectrode Arrays and Ceric Ammonium Nitrate: A Simple Strategy for Developing New Site-Selective Synthetic Methods

David Kesselring, Karl Maurer and Kevin D. Moeller
J. Am. Chem. Soc., 2008, 130 (34), 11290–11291

Conditions for a site-selective ceric ammonium nitrate oxidation have been developed. The reactions proceed nicely on both 1K- and 12K-microelectrode arrays. The procedure for developing the reactions was very simple and demonstrated that the same reagents used for a solution-phase reaction can be used for a related site-selective reaction on a microelectrode array.


July 25, 2008

Moving Known Libraries to an Addressable Array: A Site-Selective Hetero-Michael Reaction

Melissae Stuart, Karl Maurer, Kevin D. Moeller
Bioconj. Chem. 2008, 19, 1514-1517

A two-step, Michael reaction-based strategy for site-selectively placing molecules by unique electrodes in an addressable microelectrode array has been developed. The strategy is compatible with the use of polypeptide nucleophiles and works with microelectrode arrays having either 1024 electrodes/cm2 or 12544 electrodes/cm2. The chemistry should allow for the transfer of existing molecular libraries to microelectrode array devices for analysis.


May 21, 2008

Building Addressable Libraries: Site-Selective Formation of an N-Acyliminium Ion Intermediate

David Kesselring, Karl Maurer and Kevin D. Moeller
Org. Lett., 2008, 10 (12), 2501–2504

A strategy for site-selectively generating reactive N-acyliminium ion intermediates on a microelectrode array has been developed. The route capitalizes on the use of an electroauxiliary for building a methoxylated amino acid substrate, and then the electrochemical generation and solution phase confinement of acid in order to form the N-acyliminium ion. Keys to this strategy were the stability of an N-α-methoxyalkyl amide to basic reaction conditions and the generality of the electrogenerated acid conditions for conducting microelectrode array reactions in a site-selective fashion.


April 26, 2008

The Use of a Detectable, Mass-spectrometry-cleavable Linker for Quality Control on an Addressable Microelectrode Array

Ceng Chen, Peng Lu, Amy Walker, Karl Maurer, and Kevin D. Moeller
Electrochem. Commun., 2008, 10, 973–976

The synthesis, site-selective placement, and TOF-SIMS cleavage properties of a new, fluorescent linker for attaching molecules to a microelectrode array are reported. The linker was developed to provide a handle for quality control assessment of the microelectrode arrays being used to probe the binding of molecular libraries with biological receptors.