Synthesis of Imidazole-Based Functionalized Mesoionic Carbene Complexes of Palladium: Comparison of Donor Properties and Catalytic Activity toward Suzuki–Miyaura Coupling

Three different backbone-monofunctionalized imidazolium salts have been synthesized using the metal–halogen exchange procedure, and their corresponding mesoionic carbene complexes with palladium were prepared via oxidative addition without protection of the C2 position. The donor properties were evaluated with ³¹P NMR spectroscopy of the respective palladium complexes. The catalytic activity of these complexes toward Suzuki–Miyaura coupling of aryl bromides was also explored. Also, in one case, a comparison of donor properties was made with those of a “normal” carbene with similar steric bulk

Bovine insulin transport across short-term 3-day Caco-2 monolayers.

<p>Transport of active peptides was measured across the confluent Caco-2 monolayers at different loading concentrations. 0.05, 0.15, 0.6, and 1.0 mg of bovine insulin was loaded onto Caco-2 monolayer in apical chambers by dissolving the same in the culture medium. Apical-to-basolateral permeability was determined by analyzing the samples collected from basolateral chambers at different time points for up to 5 hrs. TEER values were also measured to account for the integrity of the monolayer during the experiment. Bovine insulin concentrations were measured by commercially available ELISA kits, as mentioned in the Methods section. (<b>a</b>) TEER values of Caco-2 monolayer at different loading concentrations of 0.05 (circles), 0.15 (triangles), 0.6 (diamonds), and 1.0 (crosses) mg/well of bovine insulin. (<b>b</b>) Cumulative amount of insulin transported (µg) to the basolateral chamber at different time-points at different loading concentrations of 0.05 (open circles), 0.15 (filled circles), 0.6 (filled squares), and 1.0 (open squares) mg/well. Data represent mean±SD (n = 3).</p

Synthesis, Structure, and Coordination Chemistry of Phosphine-Functionalized Imidazole/Imidazolium Salts and Cleavage of a C–P Bond in an NHC–Phosphenium Salt using a Pd(0) Precursor

A simple method involving metal–halogen exchange reaction(s) to prepare various phosphine-functionalized imidazole/imidazolium salts and their coordination chemistry with different metal precursors has been described. Interestingly, the reaction of 1,3-dimethyl-2-(diphenylphosphino)-4-iodoimidazolium iodide (<b>6</b>) with Pd₂(dba)₃ in the presence of triphenylphosphine affords a Pd­(II)–NHC complex which involves the cleavage of a C–P bond presumably occurring via oxidative addition of Pd(0) to a C–I bond to afford an in situ generated Pd­(II) species, which subsequently reacts with another 1 equiv of <b>6</b> through the phosphine center to form an adduct followed by a dephosphinylation reaction

FITC-insulin transport across Caco-2 monolayers.

<p>(<b>a</b>) Time-course study of FITC-insulin transport (mg) at different loading concentrations. FITC-insulin was loaded in apical chambers at 0.05 (open circles), 0.15 (filled circles), 0.3 (squares), and 0.6 (triangles) mg/well respectively; and permeation was measured by measuring the fluorescence in samples collected from basolateral chamber at different time-points up to 5 hrs. (<b>b</b>) % FITC-insulin transport across Caco-2 monolayers. Data represent mean±SD (n = 3).</p

Sulforhodamine-B transport across Caco-2 monolayers.

<p>(<b>a</b>) Time-course study of sulforhodamine-B transport (mg) at different loading concentrations. Sulforhodamine-B was loaded in apical chambers at 0.05 (open circles), 0.15 (filled circles), 0.3 (squares), and 0.6 (triangles) mg/well respectively; and apical-to-basolateral permeation was measured by measuring the fluorescence in samples collected from basolateral chamber at different time-points up to 5 hrs. (<b>b</b>) % Sulforhodamine-B transport across Caco-2 monolayers over of 5 hrs of incubation. Data represent mean±SD (n = 3).</p

Transport of exenatide across Caco-2 monolayers.

<p>Apical-to-basolateral permeability of exenatide was measured at different apical loading. TEER values were determined to ensure monolayer integrity. (<b>a</b>) TEER values of Caco-2 monolayer following apical loading of different concentrations of exenatide at 0.3 (circles), 1.0 (triangles), 3.0 (diamonds), and 9.0 (crosses) µg/well. (<b>b</b>) Cumulative transport of exenatide (µg) to basolateral chamber during the experiment at different apical loading concentrations of 0.3 (filled circles), 1.0 (open circles), 3.0 (squares), and 9.0 (triangles) µg/well. Data represent mean±SD (n = 3).</p

Transport of salmon Calcitonin (sCT) across Caco-2 monolayers.

<p>Permeation of salmon Calcitonin was measured at different loading concentrations. Apical-to-basolateral permeability was measured by analyzing the amount of sCT present in basolateral chamber at different time-points. TEER values were measured to validate integrity of the monolayers. sCT concentrations were measured by commercially available ELISA kits, as mentioned in the Methods section. (<b>a</b>) TEER values of Caco-2 monolayer at different sCT loading concentrations of 5.0 (circles) and 24.0 (triangles) µg/well. (<b>b</b>) Cumulative amount of calcitonin transported (µg) to the basolateral chamber at different time-points at different loading concentrations of 5.0 (open circles) and 24.0 (filled circles) µg/well. Data represent mean±SD (n = 3).</p

Permeability values under various conditions tested in this study.

<p>Data represent mean±SD (n = 3).</p

Frequency of cases with quantum of myopia progression after 1 year.

<p>Frequency of cases with quantum of myopia progression after 1 year.</p

Age specific progression of myopia (n = 1279).

<p>Age specific progression of myopia (n = 1279).</p