Biosensing interfaces consisting of linker molecules (COOH or NH2) and charged, antifouling moieties ((SO3− and N+(Me 3) for biosensing applications were prepared for the first time by the in situ deposition of mixtures of aryl diazonium cations on indium tin oxide (ITO) electrodes.
A mixture of the appropriate aryl bromides 5 (1 mmol), and phenylboronic acid (6a) (146 mg, 1.2 mmol), tetrabutylammonium bromide (194 mg, 0.6 mmol), Pd-complex 4 (0.25 mol%), KOH (112 mg, 2 mmol), and distilled water (10 mL) were mixed in the specified CEM reaction vessel HP-500.
A mixture of compound 14 (0.01 mol), appropriate aryl aldehydes 4a b (0.01 mol) in ethanol (30 mL) with catalytic amount of piperidine was heated under reflux for 3 h.
Furthermore, a competition experiment involving a 1 1 mixture of 1 b and its aryl-deuterium labelled analogue [D5] 1 b (Scheme 5 b) showed no kinetic isotope effect, suggesting that rearomatisation is not the rate-determining step.
Hence, we were interested in the investigation of alternative methods suitable for aryl halides, and we developed a RuII-catalyzed method that enabled the use of aryl bromides and aryl iodides as arylation reagents.
We used an equimolar mixture of unsubstituted and para-substituted starting material with our optimized reaction conditions; this mixture was treated with 1 equiv. of bromobenzene, a decreased amount of aryl source in comparison to previous experiments to ensure incomplete conversion of both substrates.
A mixture of diphenyl pyrazolone 1 (0.01 mol), appropriate aryl aldehydes 4a b (0.01 mol) in ethanol (30 mL) with catalytic amount of piperidine was heated under reflux for 3 h.
The quantitative formation of aryl sulfonium salt 13 was confirmed by HPLC-mass spectrometric comparison of the crude product mixture with authentic samples of sulfonium salt 13 of known concentration (see the Supporting Information).
One electron reduction of aryl halides is known to generate the aryl radical and halide ion.
Scheme 1 Proposed mechanism for synthesis of aryl thioethers.
