Syringe thin layer chromatography

Yields sometimes drop when an old bottle of borane-dimethyl sulfide is used. Reaction progress can be monitored by thin layer chromatography (silica gel, eluting with 10 10 1 chloroform-methanol-concentrated ammonium hydroxide). Any remaining phenylalanine stains heavily when exposed to ninhydrin (Rf 0.35). If phenylalanine is detected after 5 hr of reflux, an additional 10 ml (0.10 mol) of borane-dimethyl sulfide is added via syringe, and the solution is heated at reflux for 1 additional hr. 

To the solution of 5.35 g (28 mmol) [3-(lH-benzimidazol-2-yl)propyl]methylamine in 12.5 mL toluene was added by syringe 12.5 mL (11.42 g, 114 mmol) isopropenyl acetate. The reaction mixture was heated to reflux temperature, and stirred at that temperature for 1.75 hours, with reaction completion monitored by thin-layer chromatography (silica gel, eluting with 70% ethyl acetate/30% methanol). The product, N-[3-(lH-benzimidazol-2-yl)propyl]-N-methylacetamide, was obtained in quantitative yield. 

Apply the mixture of compounds as a dichloromethane solution to a preparative thin-layer chromatography plate using a syringe. Allow the plate to air-dry, and then elute it with ethyl acetate. 

Zinc dust (325 mesh, 0.147 g, 2.25 mmol, 3 equiv.) was weighed into a 50-niL round-bottomed flask with side arm, which was repeatedly evacuated, heated using a hot air gun, and flushed with nitrogen. Dry DMF (0.5 mL) and trimethylsilyl chloride (6 pL, 0.046 mmol) were added, and the resultant mixture was stirred for 30 min at room temperature. Iodide (0.75 mmol) was dissolved in dry DMF (0.5 mL) under nitrogen. The iodide solution was transferred via a syringe to the zinc suspension at 0 °C, and the mixture was then stirred. Thin layer chromatography (TLC) analysis (petroleum ether-ethyl acetate, 2 1) showed complete consumption of the iodide within 5-60 min. 

S)-binap (63 mg, 1.0 mmol), and Pd2(dba)3 (30 mg, 0.3 mmol). Toluene (air-free, anhydrous) was added via syringe and the reaction mixture was heated to 75 - 85 °C. The reaction mixture was stirred under an atmosphere of nitrogen and monitored periodically by thin layer chromatography (TLC) using silica gel plates (fluorescent indicator) with an eluent of 10 % methanol in methylene chloride. 

Plates for thin layer chromatography UV fluorescence spectrophotometer Circulating air drying cabinet 60 C Microlitre syringe, 50 pi... 

The instrament Linomat 5 is fully controllable by the winCATS-Planar Chromatography Manager software. With this system, one can select various parameters, such as number of tracks, band length, and application volume sequence, x positions on the plates, track distances, as well as application methods. The instrument applies the samples onto a thin layer automatically however, only changing the sample, i.e., filling and rinsing the syringe, is carried out manually. ... 

---