Synthesis and characterization of a new surface derivatizing reagent to promote the adhesion of polypyrrole films to N-type silicon photoanodes: N-(3-(trimethoxysilyl)propyl)pyrrole

Abstract

J . Am. Chem. SOC. natural tylosin (vide infra). To complete the synthesis, 6 was selectively reduced (4.0 equiv of Dibal, CH2C12, -78 "C, reduction of dienone and y-lactone) and oxidized (1.3 equiv of DDQ, benzene, 25 "C) to produce 0-mycinosyltylonolide (1) in 76% overall yield. Synthetic 1 was identical in all respects with an authentic sample obtained by degradation of tylosin as described below.Mild acid hydrolysis of tylosin (7) (Scheme I) (dilute HC1, THF, 25 OC or AcOH-THF-H20, 25 "C) detaches only mycarose from the molecule producing 0-mycinosyl-0-mycaminosyltylonolide (8) in 90% yield.I0 Both the highly methoxylated mycinose and the basic, N-containing mycaminose are resistant to acid hydrolysis under normal conditions that will allow survival of the rest of the molecule. A Polonovski type degradation of 8 [(a) 1.1 equiv of m-CPBA, CH2C12, 0 OC, 0.5 h followed by 8.0 equiv of (CF3C0),0 and 8.0 equiv of pyridine, 0 "C, 0.5 h and then aqueous KHC03 workup and 1 .O equiv of anhydrous K2C03, MeOH, 0 "C, 1 h)], however, furnished 0-mycinosyltylonolide (1) in 76% yield after chromatographic purification. The same compound (1) was also produced by direct degradation of tylosin (7) under the above conditions (65% yield)." M n 0 2 (excess, CH2C12, 48 h) oxidation of 0-mycinosyltylonolide (1) led to compound 6 in high yield (87%).So that the potential of Omycinosyltylonolide (1) as a precursor to tylosin (7) could be demonstrated, a number of final chemical maneuvers were performed. Thus, reaction of (1) with ethylene glycol in the presence of camphorsulfonic acid as catalyst yielded the acetal 9 as a major product (65%),12 liberating the C-5 hydroxyl for selective glycosidation. Although molecular models as well as chemical evidence indicate that no protection of the C-3 hydroxyl group should be needed, protection of the mycinose-bound hydroxyl might be necessary for steric-reactivity reasons for such glycoside formation attempts. Selective blockade of this hydroxyl was, therefore, sought and achieved by treating 9 sequentially with (a) phenylboronic acid (1.2 equiv, benzene, azeotropic removal of water at reflux to form a cyclic boronate ester at C-3 and C-5), (b) tert-butyldimethylsilyl chloride (excess imidazole, DMF, 25 "C), and (c) acetone-H,O (3:1, 25 "C, 1 h) to remove the boronate furnishing compound 10 in 72% overall yield.This highly efficient and stereocontrolled total synthesis of Omycinosyltylonolide (1) clearly demonstrates the advantageous utilization of carbohydrates in the construction of the 16-membered ring macrolide antibiotic^.'^-'^ At present, no practical methodology exists for completing the remaining disaccharide, mycaminose-containing unit, due to the well-recognized problems of glycosidation of N-containing sugars.I6 New strategies directed toward this goal are currently under way in these laboratories.Four research groups have suggested that "polypyrrole"' formed by anodic polymerization of pyrrole, eq 1, can be used to protect '0 0.3 positive M [ E t q N ] E F q / C H~C~ potential

Electropolymerized Self‐Assembled Monolayers of a 3,4‐Ethylenedioxythiophene‐Thiophene Hybrid System

“…The immobilization of electroactive p-conjugated systems on gold surfaces by formation of self-assembled monolayers (SAMs) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] has recently become a focus of high interest motivated by their potential applications in the field of functionalized surfaces, [1] sensors, [2] molecular electronics, [3] or molecular heterojunctions for photovoltaic conversion. [4] On the other hand, several groups have reported the use of surface-immobilized electropolymerizable systems as starting point for the deposition of electrogenerated electroactive conducting polymers.…”

“…[4] On the other hand, several groups have reported the use of surface-immobilized electropolymerizable systems as starting point for the deposition of electrogenerated electroactive conducting polymers. [5][6][7][8][9][10][11][12] Wrighton and coworkers used pyrrole attached on silicon by a silane group to promote the adhesion of subsequently electropolymerized poly(pyrrole). [6] More recently, this method has been extended to other systems such as pyrrole-containing dendrimers, [7] aniline, [8] carbazole, [9] thiophene, and oligothiophenes derivatives.…”

The application of ferrocene‐modified n‐type silicon in glucose biosensors

“…The method used in this study was essentially that reported by Simon et al [9]. Briefly, after drying at 80"C, the etched electrodes were placed inside dry flat-bottomed glass tubes containing small magnetic followers.…”

Synthesis and Characterization of New Adhesion Promoter for Grafting Conducting Polymer on Oxide Substrate

“…8 Up to now, several studies reported on using pyrrole-functionalized organosilanes to increase the adhesion of the polymers to the substrate. For example, 3-(pyrrol-1-yl) propyl trimethoxylsilane was successfully used by Simon et al 9 and Wu et al 10 for adhering PPy on silicon substrate; Cossement obtained dense and adhesive PPy films by grafting polypyrrole on the 6-(pyrrol-1-yl)-n-hexyl trichlorosilane modified ITO electrode; 11 Guiseppi-Elie et al 5 and Faverolle et al 12 used other pyrrole-substituted organosilane monolayers for grafting PPy on SiO 2 substrates; Shustak et al 13 used n-alkanoic acid monolayer to promote the adhesion of polypyrrole on stainless steel. However, all above mentioned adhesion promoters are 1-substituted pyrrole organosilane.…”