US20060189166A1

US20060189166A1 - Process for performing an isolated Pd(II)-mediated oxidation reaction

Info

Publication number: US20060189166A1
Application number: US11/063,402
Authority: US
Inventors: Eden Tesfu; Karl Maurer; Kevin Moeller
Original assignee: Combimatrix Corp
Current assignee: Washington University in St Louis WUSTL; Customarray Inc
Priority date: 2005-02-22
Filing date: 2005-02-22
Publication date: 2006-08-24
Also published as: WO2006091662A3; WO2006091662A2; US20060205959A1; US7507837B2

Abstract

There is disclosed a process for performing an isolated Pd(II) mediated oxidation reaction electrochemically. The inventive process is performed on an electrode array device having a plurality of separately addressable electrodes. Preferably, the Pd(II) mediated oxidation is a Wacker reaction. Specifically, there is disclosed a process for conducting an isolated Pd(II) mediated oxidation on a plurality of electrodes, comprising providing an electrode array device having a plurality of electrodes with a conductive electrode surface and a matrix or coating material over the electrodes surfaces; providing a solution bathing the electrode array matrix or coating material and electrode surfaces, wherein the solution comprises a transition metal species and a confining agent; and biasing one or a plurality of electrodes (“selected electrode or electrodes”) with a voltage or current to regenerate the transition metal species required for the isolated Pd(II) mediated oxidation, whereby the confining agent limits diffusion of the transition metal species to a volume surrounding each selected electrode surface.

Description

TECHNICAL FIELD OF THE INVENTION

The present invention provides a process for performing an isolated Pd(II) mediated oxidation reaction electrochemically. The inventive process is also performed on an electrode array device having a plurality of separately addressable electrodes. Preferably, the Pd(II) mediated oxidation is a Wacker reaction. Specifically, the inventive process provides a process for conducting an isolated Pd(II) mediated oxidation on a plurality of electrodes, comprising providing an electrode array device having a plurality of electrodes with a conductive electrode surface and a matrix or coating material over the electrodes surfaces; providing a solution bathing the electrode array matrix or coating material and electrode surfaces, wherein the solution comprises a transition metal species and a confining agent; and biasing one or a plurality of electrodes (“selected electrode or electrodes”) with a voltage or current to regenerate the transition metal species required for the isolated Pd(II) mediated oxidation, whereby the confining agent limits diffusion of the transition metal species to a volume surrounding each selected electrode surface.

BACKGROUND OF THE INVENTION

Electronically addressable chip-based molecular libraries (Lipshutz et al., Nature Genetics, 21:20, 1999; Pirrung, Chem. Rev. 97:473, 1997; Webb et al., J. Steroid Biochem. Mol. Biology, 85:183, 2003; Shih et al., J. Virological Methods, 111 :55, 2003) have long been desired but have not been created. CombiMatrix Corporation scientists have been utilizing active-semiconductor electrode arrays that incorporate individually addressable microelectrodes to synthesize oligonucleotide and polypeptide molecules (U.S. Pat. No. 6,093,302; WO/0053625; Oleinikov et al., J. Proteome Res., 2:313, 2003; Sullivan et al., Anal. Chem., 71:369, 1999; Zhang et al., Anal. Chim. Acta, 421:175, 2000; and Hintsche et al., Electroanal. 12:660, 2000).
In this way, each unique set of molecules in a library can be located proximal to a selected electrode or set of electrodes that can, in turn, be used to monitor their behavior (Dill et al., Analytica Chimica Acta, 444:69, 2001). This is accomplished by coating the electrode-containing array devices with a porous polymer and then utilizing the electrodes to both attach monomers to the electrode array devices and then generate reagents capable of performing reactions on the monomers.
Pd(II) mediated oxidations are powerful synthetic tools that allow for the selective functionalization of organic molecules. Therefore, there is a need in the art for a combinatorial chemical synthesis device that could perform Pd(II) mediated oxidations on an electrode array. In particular, to perform a Pd(II) mediated oxidation on a selected electrode on the device. As a proof of principle, a Wacker oxidation (conversion of an alkene to a ketone) was used for this purpose. Such a device and process would expand the number of different molecules that could be constructed. Such a tool would allow for massively parallel electrochemical synthesis in small volumes on an electrode array device and create arrays containing highly diverse libraries of chemical compounds that are different from each other yet synthesized in parallel. Such “combinatorial libraries” could be synthesized rapidly, in small volumes and with high diversity.
Therefore, there is a need in the art to be able to perform rapid and diverse synthesis of chemical libraries on an electrode array device for large scale screening of combinatorial libraries. The present invention was made to address this need in the art.

SUMMARY OF THE INVENTION

The present invention provides a process for conducting an isolated Pd(II) mediated reaction on a plurality of electrodes, comprising:
(a) providing an electrode array device having a plurality of metallic or conductive electrodes each with a conductive surface, and having a matrix or coating material over the electrodes surfaces;
(b) providing a solution bathing the electrode array device, wherein the solution comprises a transition metal species and a confining agent; and
(c) biasing one or a plurality of electrodes (selected electrode or electrodes) on the electrode array device with a voltage or current to regenerate the transition metal species consumed during the Pd(II)-mediated reaction, whereby the confining agent limits diffusion of the transition metal species to a volume surrounding each selected electrode surface.
Preferably, the isolated Pd(II) mediated oxidation is selected from the group consisting of a Wacker reaction, a Saegusa reaction, oxidative aryl coupling reactions, alkene to π-allyl palladium conversions, enol ether—organometallic coupling reactions, and any other stoichiometric Pd(II) oxidation (for a summary see: “Chapter 3. Oxidative Reactions with Pd(II) Compounds” in Palladium Reagents and Catalysts, Tsuji, J.; John Wiley and Sons; West Sussex, England; 1995, pp 19-108).
Preferably, the transition metal is a Pd (II) containing species. Most preferably, the transition metal is Pd(OAc)₂. Preferably, the Pd(II) species is generated by oxidation from Pd(0) by an intermediate oxidant generated by a regeneration reaction at a selected electrode. Most preferably, the intermediate oxidant species is a triarylamine cation radical generated from a triaryl amine at the electrode. Preferably, the confining agent is a reductant added to the solution sufficient to convert Pd(II) back to Pd(0) in areas not proximal to an activated electrode. Most preferably, the confining agent is a reductant selected from the group consisting of substituted or an unsubstituted alkyl vinyl ethers, divinyl ether, aryl vinyl ether, alkene, H₂, hydroquinones, and combinations thereof More preferably, the confining agent is a substituted or an unsubstituted vinyl alkyl ether, wherein the alkyl moiety is a C_1-8alkyl group. Preferably, the biasing step uses a voltage no greater than 5V. Preferably, the biasing step was performed for a time of from about 1 sec to about 10 min using a pulsed voltage or nonpulsed voltage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Shows a picture of an array produced in the experiment of example #1, the bright spots are locations which were oxidized via the Wacker reaction and stained as specified, the dark spots are electrodes that were not utilized for the oxidation (the Pt electrodes block the background fluorescent originating from the chip itself).
FIG. 2 shows a schematic of the Wacker reaction as preformed in example 1.
FIG. 3 shows the experimental procedure used in example 1.

DETAILED DESCRIPTION OF THE INVENTION

In the exemplified experiments Pd(0) was oxidized to Pd(II) at selected electrodes on the electrode array device. Further, a confining agent was necessary to confine the reaction to the region surrounding a selected electrode, to preserve the fidelity of the combinatorial reaction scheme (that is, confining the reaction to the region in the porous matrix above the selected electrode and not to a neighboring unselected electrode). Ethyl vinyl ether was a preferred confining agent. This is because the reaction performed without the preferred confining agent, ethyl vinyl ether, led to significant spreading of signal away from selected electrode sites.
Additionally, since the Wacker reaction allows the generation of a ketone or an aldehyde (or a mixture of both) at a selective location this selectively produced ketone can be used to selectively immobilize an amine moiety on a biological molecule. (“Immobilization of Enzymes and Cells” by Bickerstaff 1997 Humana Press; and Pierce applications handbook 2003 p 137). Therefore, the present invention further provides a process for selectively immobilizing a biological molecule having a free amine moiety onto a selected region of a porous matrix, comprising:
(a) providing an electrode array device having a plurality of metallic or conductive electrodes each with a conductive surface;
(b) providing a solution bathing the electrode array device, wherein the solution comprises a Pd(II) metal species and a confining agent;
(c) biasing one or a plurality of selected electrodes on the electrode array device with a voltage or current to perform a Wacker reaction generating the Pd(II) metal species consumed during the Wacker reaction and generating a free ketone or a free aldehyde moiety or a mixture of both, whereby the confining agent limits diffusion of the transition metal species to a volume surrounding each selected electrode surface; and
(d) providing a biological material having a free amino moiety to the electrode array device to selectively immobilize to the porous matrix located adjacent to the selected electrode(s).
Preferably, the Pd(II) species is generated by oxidation from Pd(0) by an intermediate oxidant generated by a regeneration reaction at a selected electrode. Most preferably the intermediate oxidant species is a triarylamine cation radical generated from a triaryl amine at the electrode. Preferably, the confining agent is a reductant added to the solution sufficient to convert Pd(II) back to Pd(0) in areas not proximal to an activated electrode. Most preferably, the confining agent is a reductant selected from the group consisting of substituted or unsubstituted alkyl vinyl ethers, divinyl ether, aryl vinyl ether, alkene, H₂, hydroquinones, and combinations thereof. More preferably, the confining agent is a substituted or unsubstituted alkyl vinyl ether, wherein the alkyl moiety is a C_1-8alkyl group. Preferably, the biasing step uses a voltage no greater than 5V. Preferably, the biasing step was performed for a time of from about 1 sec to about 10 min using a pulsed voltage or nonpulsed voltage.
The reagents generated at any given electrode were confined to the area surrounding the electrode. The confinement was accomplished by placing a substrate in the solution bathing the electrode array surface. The substrate “consumed” the reagent. For example, substrates that “consume” reagents include acids that consume bases, bases that consume acids, Pd(II) consumed with ethyl vinyl ether, allyl alkyl carbonate consuming Pd(0) and the like. Briefly, this process was described in connection with the generation of acids and bases confined to a volume on electrode array devices (see, for example, Montgomery U.S. Pat. No. 6,093,302, the disclosure of which is incorporated by reference herein). In other work, generation of a Pd(0) reagent was confined to the area proximal to the active electrode (patent application submitted).
The present invention was motivated by the desire to determine if the electrodes on an electrode array device could be used as anodes in the oxidation of Pd(0) to Pd(II) in order to use Pd(II) as a reagent at pre-selected sites on an electrode array device having a plurality of electrode sites (each separately addressable). The problem solved by the present invention was to find an efficient confinement strategy for the Pd(II) reagent generated so that it was confined to one electrode and did not cause a reaction at a neighboring electrode. This is necessary in order to be able to perform a transformation at one site without causing cross contamination with materials produced in other locations of the array.
In the case of Pd(0), Pd(0) was used to catalyze a reaction between an aryl iodide and an acrylate ester. Hence, most of the reagent generated at a selected electrode on an electrode array was not consumed by the reaction. Methyl allyl carbonate was used as a confining agent to react with any Pd(0) reagent leaving the vicinity of the active electrodes there by preventing its catalyzing the reaction in undesired location. (Process for Performing an Isolated Heck Reaction Electrochemicaly on an Electrode Array Device Patent applied for Jan. 7, 2005 the disclosure of which is incorporated by reference herein).
In a preferred embodiment of the Pd(II) case, (for example a Wacker oxidation) the reagent which is generated is a Pd(II) species which is reduced to Pd(0) during the reaction process and is recycled by triarylamine radical cation generated at the electrode. The confining agent (ethyl vinyl ether) reacts with any Pd(II) reagent leaving the vicinity of the electrode, reducing it to Pd(0) which does not perform the Wacker oxidation (conversion of an alkene to a carbonyl compound), thereby preventing unwanted reaction at unactivated locations.
The present invention provides a process for conducting a parallel Wacker reaction on a plurality of electrodes, comprising
(a) providing an electrode array device having a matrix or coating material over metallic or conductive electrodes surfaces and a plurality of electrodes;
(b) providing a solution bathing the electrode array device, wherein the solution comprises a transition metal species, solvent, and a confining agent; and
(c) biasing one or a plurality of electrodes on the electrode array device with a voltage or current to regenerate the transition metal species consumed during the Wacker reaction, whereby the confining agent limits diffusion of the transition metal species to a volume surrounding each selected electrode surface.
The present invention further provides a process for conducting an isolated Pd(II) mediated reaction on a plurality of electrodes, comprising:
(a) providing an electrode array device having a matrix or coating material over metallic or conductive electrodes surfaces and a plurality of electrodes;
(b) providing a solution bathing the electrode array device, wherein the solution comprises a transition metal species, solvent, and a confining agent;
(c) biasing one or a plurality of electrodes on the electrode array device with a voltage or current to regenerate the transition metal species consumed during the Pd(II) mediated reaction, whereby the confining agent limits diffusion of the transition metal species to a volume surrounding each selected electrode surface.
Preferably, the isolated Pd(II) mediated oxidation is selected from the group consisting of a Wacker reaction, a Saegusa reaction, oxidative aryl coupling reactions, alkene to π-allyl palladium conversions, enol ether—organometallic coupling reactions, and any other stoichiometric Pd(II) oxidation (for a summary see: “Chapter 3. Oxidative Reactions with Pd(II) Compounds” in Palladium Reagents and Catalysts, Tsuji, J.; John Wiley and Sons; West Sussex, England; 1995, pp 19-108). Preferably, a Pd (II) species is stabilized with ligands. Preferably, the confining agent is an reductant added to solution sufficient to convert Pd(II) back to Pd(0) in areas not near to an active electrode. Most preferably, the confining agent is a reductant selected from the group consisting of substituted or unsubstituted alkyl vinyl ether, divinyl ether, aryl vinyl ether, alkene, H₂, hydroquinone, and combinations thereof. More preferably, the confining agent is a substituted or unsubstituted alkyl vinyl ether wherein the alkyl moiety can be a C_1-8alkyl group. Preferably, the biasing step used a voltage no greater than 5 V. Preferably, the biasing step was performed for a time of from about 1 sec to 10 min.
Preferably, the transition metal reagent for the Wacker reaction is a palladium Pd(OAc)₂.
The term “substituted” or “substitution,” in the context of a moiety of the confining agent, means a moiety independently selected from the group consisting of (1) the replacement of a hydrogen on at least one carbon by a monovalent radical, (2) the replacement of two hydrogens on at least one carbon by a divalent radical, (3) the replacement of three hydrogens on at least one terminal carbon (methyl group) by a trivalent radical, (4) the replacement of at least one carbon and the associated hydrogens (e.g., methylene group) by a divalent, trivalent, or tetravalent radical, and (5) combinations thereof. Meeting valence requirements restricts substitution. Substitution occurs on alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, cycloalkynyl, aryl, heterocyclic ring, and polycyclic groups, providing substituted alkyl, substituted alkenyl, substituted alkynyl, substituted cycloalkyl, substituted cycloalkenyl, substituted cycloalkynyl, substituted aryl group, substituted heterocyclic ring, and substituted polycyclic groups.
The groups that are substituted on an alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, cycloalkynyl, aryl, heterocyclic ring, and polycyclic groups are independently selected from the group consisting of alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, cycloalkynyl, aryl, heterocyclic ring, polycyclic group, halo, heteroatom group, oxy, oxo, carbonyl, amide, alkoxy, acyl, acyloxy, oxycarbonyl, acyloxycarbonyl, alkoxycarbonyloxy, carboxy, imino, amino, secondary amino, tertiary amino, hydrazi, hydrazino, hydrazono, hydroxyimino, azido, azoxy, alkazoxy, cyano, isocyano, cyanato, isocyanato, thiocyanato, fulminato, isothiocyanato, isoselenocyanato, selenocyanato, carboxyamido, acylimino, nitroso, aminooxy, carboximidoyl, hydrazonoyl, oxime, acylhydrazino, amidino, sulfide, thiol, sulfoxide, thiosulfoxide, sulfone, thiosulfone, sulfate, thiosulfate, hydroxyl, formyl, hydroxyperoxy, hydroperoxy, peroxy acid, carbamoyl, trimethyl silyl, nitrilo, nitro, aci-nitro, nitroso, semicarbazono, oxamoyl, pentazolyl, seleno, thiooxi, sulfamoyl, sulfenamoyl, sulfeno, sulfinamoyl, sulfino, sulfinyl, sulfo, sulfoamino, sulfonato, sulfonyl, sulfonyldioxy, hydrothiol, tetrazolyl, thiocarbamoyl, thiocarbazono, thiocarbodiazono, thiocarbonohydrazido, thiocarbonyl, thiocarboxy, thiocyanato, thioformyl, thioacyl, thiosemicarbazido, thiosulfino, thiosulfo, thioureido, thioxo, triazano, triazeno, triazinyl, trithio, trithiosulfo, sulfinimidic acid, sulfonimidic acid, sulfinohydrazonic acid, sulfonohydrazonic acid, sulfinohydroximic acid, sulfonohydroximic acid, and phosphoric acid ester, and combinations thereof.
As an example of a substitution, replacement of one hydrogen or ethane by a hydroxyl provides ethanol, and replacement of two hydogens by an oxo on the middle carbon of propane provides acetone (dimethyl ketone.) As a further example, replacement the middle carbon (the methenyl group) of propane by the oxy radical (—O—) provides dimethyl ether (CH₃—O—CH₃.) As a futher example, replacement of one hydrogen on a benzene by a phenyl group provides biphenyl. As provided above, heteroatom groups can be substituted inside an alkyl, alkenyl, or alkylnyl group for a methylene group (:CH₂) thus forming a linear or branched substituted structure rather than a ring or can be substituted for a methylene inside of a cycloalkyl, cycloalkenyl, or cycloalkynyl ring thus forming a heterocyclic ring. As a further example, nitrilo (—N═) can be substituted on benzene for one of the carbons and associated hydrogen to provide pyridine, or and oxy radical can be substituted to provide pyran.
The term “unsubstituted” means that no hydrogen or carbon has been replaced on an alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, cycloalkynyl, or aryl group.
The following example supports the conclusion that a Wacker reaction (that is a preferred Pd(II) mediated reaction) has been performed at pre-selected sites on an electrochemically-addressable electrode array device. The experiment highlights the utility of a Pd(II) reagent on the electrode array device, and for the first time demonstrates the potential for employing a Pd(II) reagent to selectively construct molecules proximal to specific addressable electrodes.

EXAMPLE 1

This example tested the feasibility of the inventive process. In order to test the effectiveness of this approach, an electrode array device with a surface area of about 1 cm²and having 1024 individually addressable platinum electrodes, was coated with a porous hydroxylated polymer membrane, and then treated with the N-hydroxysuccinic ester of 10-undecenoic acid as outlined in FIG. 3. The substrate was concentrated on the electrode array device in the region close to the electrodes by catalyzing the reactions with an electrogenerated base (“Electrogenerated Bases.” Utley and Nielsen in Organic Electrochemistry: Fourth Edition Lund; Hammerich Ed.; Marcel Dekker: New York, p 1227, 2001). The base was formed by using the electrodes on the electrode array device to reduce vitamin B₁₂(WO00/53625). To accomplish this, the electrode array device was submerged (along with a Pt-rod counter electrode) into a tetrabutylammonium nitrate in DMF/MeOH electrolyte solution containing the vitamin B₁₂. Selected electrodes were poised at a potential difference of −2.4 volts versus the Pt counter electrode for 0.5 second and off for 0.1 second for 300 cycles. These conditions were selected in analogy to earlier coupling reactions using the same electrode array devices in order to ensure selectivity (longer times generate larger quantities of reagent and more chance for migration to neighboring electrodes) and complete coverage of the electrode (extra cycles). Following the coupling reaction, any free hydroxyls remaining on the surface of the electrode array device were capped by exposing the electrode array device to acetic anhydride using the same electrogenerated base conditions.
A Wacker oxidation, outlined in FIG. 2, was then performed at selected electrodes by reversing the electrode polarity and utilizing them as anodes. Electrodes not selected for the Wacker oxidation were simply turned off. For this experiment, the electrode array device and counter electrode were submerged in 2.5 mL of 0.5 M Et₄NOTs in 7:1 acetonitrile/water electrolyte solution containing 32 μg of Pd(OAc)₂, 1.39 mg of tris-2-bromophenylamine, and 83 μL of ethyl vinyl ether. The oxidation reaction was performed by pulsing the selected electrodes for 0.5 second at +2.4 V and 0.5 second at 0 V for either 300 or 600 cycles. The selected electrodes were chosen in order to form a checkerboard pattern on the electrode array device.
Once this experiment was completed, the ketones that were generated were converted to their 2,4-DNP derivatives by treating the electrode array device with a 0.5% DNP in 2N HCl solution and the electrode array device was incubated with a 5% BSA in PBS buffer solution containing commercially available rabbit anti-2,4-dinitrophenol antibody that is conjugated to the fluorescent probe Alexa Fluor® 488 (Molecular Probes (A-11097), Eugene, Oreg.) at 1/16 antibody to buffer (Conrad et al., Biological Procedures Online 2:1, 2000 and Yuan et al., Blood 84, 632, 1994). Next, the surface of the electrode array device was washed with PBS buffer to remove excess antibody and the electrode array device was imaged with an epifluorescence microscope using a blue filter (PBS buffer was needed on the surface of the electrode array device in order to ensure a successful image). The image shown in FIG. 1 shows that the experiment worked perfectly. It appears the reaction led only to the formation of ketones at the selected electrodes as demonstrated by the checkerboard pattern of fluorescence (indicated by the bright spots) on the electrode array device. In FIG. 1, the dark spots are electrodes that were not utilized for the oxidation (the Pt electrodes block the background fluorescent originating from the electrode array device itself).
Subsequent control experiments yielded two important observations about this first experiment. First, when Pd(II) was generated at selected electrodes on an electrode array device without the olefin substrate, a faint checkerboard pattern was still observed. It appears that the acetic anhydride capping step was not completely effective and Pd(II) generated at the electrode led to oxidation of the unprotected alcohols in the polymer membrane (Muzart, Tetrahedron 59:5789, 2003). An additional experiment compared “side-by-side” electrodes that had associated olefin substrate and electrodes that were devoid of any olefin substrate. In this experiment, the intensity of the fluorescent spots was significantly greater for the electrodes having the olefin substrate present. This indicates that the intensity of the fluorescent spots in the initial experiment (FIG. 1) was due primarily to the initially planned Wacker oxidation.
In a second control experiment, the ethyl vinyl ether was removed from the solution over the electrode array device. In this case, the experiment led to fluorescence seen at many electrodes that were not utilized for the oxidation as well as at a variety of random sites on the surface of the electrode array device. These data show that the use of ethyl vinyl ether was required for confining the Pd(II) to the selected electrode sites on the electrode array device.

Claims

1. A process for conducting an isolated Pd(II) mediated reaction on a plurality of electrodes, comprising:

(a) providing an electrode array device having a plurality of metallic or conductive electrodes each with a conductive surface, and having a matrix or coating material over the electrodes surfaces;

(b) providing a solution bathing the electrode array device, wherein the solution comprises a transition metal species and a confining agent; and

(c) biasing one or a plurality of electrodes (selected electrode or electrodes) on the electrode array device with a voltage or current to regenerate the transition metal species consumed during the Pd(II)-mediated reaction, whereby the confining agent limits diffusion of the transition metal species to a volume surrounding each selected electrode surface.

2. The process for conducting an isolated Pd(II) mediated reaction on a plurality of electrodes of claim 1 wherein the isolated Pd(II) mediated reaction is selected from the group consisting of a Wacker reaction, a Saegusa reaction, oxidative aryl coupling reactions, alkene to π-allyl palladium conversions, enol ether—organometallic coupling reactions, any other stoichiometric Pd(II) oxidation, and combinations thereof.

3. The process for conducting an isolated Pd(II) mediated reaction on a plurality of electrodes of claim 1 wherein the transition metal is a Pd (II) containing species.

4. The process for conducting an isolated Pd(II) mediated reaction on a plurality of electrodes of claim 3 wherein the transition metal is Pd(OAc)₂.

5. The process for conducting an isolated Pd(II) mediated reaction on a plurality of electrodes of claim 1 wherein the Pd(II) species is regenerated by oxidation from Pd(0) by an intermediate oxident generated by a regeneration reaction at a selected electrode.

6. The process for conducting an isolated Pd(II) mediated reaction on a plurality of electrodes of claim 5 wherein the intermediate oxidant species is a triarylamine cation radical generated from a triaryl amine at the electrode.

7. The process for conducting an isolated Pd(II) mediated reaction on a plurality of electrodes of claim 1 wherein the confining agent is a reductant added to the solution sufficient to convert Pd(II) back to Pd(0) in areas not proximal to an activated electrode.

8. The process for conducting an isolated Pd(II) mediated reaction on a plurality of electrodes of claim 7 wherein the confining agent is a reductant selected from the group consisting of substituted or unsubstituted alkyl vinyl ethers, divinyl ether, aryl vinyl ether, alkene, H₂, hydroquinones, and combinations thereof.

9. The process for conducting an isolated Pd(II) mediated reaction on a plurality of electrodes of claim 8 wherein the confining agent is a substituted or unsubstituted alkyl vinyl ether, wherein the alkyl moiety is a C_1-8alkyl group.

10. The process for conducting an isolated Pd(II) mediated reaction on a plurality of electrodes of claim 1 wherein the biasing step uses a voltage no greater than 5V.

11. The process for conducting an isolated Pd(II) mediated reaction on a plurality of electrodes of claim 1 wherein the biasing step was performed for a time of from about 1 sec to about 10 min using a pulsed voltage or nonpulsed voltage.

12. A process for selectively immobilizing a biological molecule having a free amine moiety onto a selected region of a porous matrix, comprising:

(a) providing an electrode array device having a plurality of metallic or conductive electrodes each with a conductive surface;

(b) providing a solution bathing the electrode array device, wherein the solution comprises a Pd(II) metal species and a confining agent;

(c) biasing one or a plurality of selected electrodes on the electrode array device with a voltage or current to perform a Wacker reaction regenerating the Pd(II) metal species consumed during the Wacker reaction and generating a free ketone or a free aldehyde moiety or a mixture of both, whereby the confining agent limits diffusion of the transition metal species to a volume surrounding each selected electrode surface; and

(d) providing a biological material having a free amino moiety to the electrode array device to selectively immobilize to the porous matrix located adjacent to the selected electrode(s).

13. The process for selectively immobilizing a biological molecule having a free amine moiety onto a selected region of a porous matrix of claim 12 wherein

14. The process for selectively immobilizing a biological molecule having a free amine moiety onto a selected region of a porous matrix of claim 12 wherein the Pd(II) species is regenerated by oxidation from Pd(0) by an intermediate oxident generated by a regeneration reaction at a selected electrode.

15. The process for selectively immobilizing a biological molecule having a free amine moiety onto a selected region of a porous matrix of claim 14 wherein the intermediate oxidant species is a triarylamine cation radical generated from a triaryl amine at the electrode.

16. The process for selectively immobilizing a biological molecule having a free amine moiety onto a selected region of a porous matrix of claim 12 wherein the confining agent is a reductant added to the solution sufficient to convert Pd(II) back to Pd(0) in areas not proximal to an activated electrode.

17. The process for selectively immobilizing a biological molecule having a free amine moiety onto a selected region of a porous matrix of claim 16 wherein the confining agent is a reductant selected from the group consisting of substituted or unsubstituted alkyl vinyl ethers, divinyl ether, aryl vinyl ether, alkene, H₂, hydroquinones, and combinations thereof.

18. The process for selectively immobilizing a biological molecule having a free amine moiety onto a selected region of a porous matrix of claim 16 wherein the confining agent is a substituted or unsubstituted vinyl alkyl ether, wherein the alkyl moiety is a C_1-8alkyl group.

19. A process for conducting a parallel Wacker reaction on a plurality of electrodes, comprising:

(a) providing an electrode array device having a matrix or coating material over metallic or conductive electrodes surfaces and a plurality of electrodes;

(b) providing a solution bathing the electrode array device, wherein the solution comprises a transition metal species, solvent, and a confining agent; and

(c) biasing one or a plurality of electrodes on the electrode array device with a voltage or current to regenerate the transition metal species consumed during the Wacker reaction, whereby the confining agent limits diffusion of the transition metal species to a volume surrounding each selected electrode surface.

20. The process for conducting a parallel Wacker reaction on a plurality of electrodes of claim 19 wherein the transition metal reagent for the Wacker reaction is a palladium Pd(OAc)₂.