Part A. A suspension of 4,5-bis(4-methoxyphenyl)-2-mercapto-1H-imidazole (10.4 g, 33.2 mmol), ethyl 5-bromovalerate (5.00 mL, 31.6 mmol), potassium carbonate (5.50 g, 39.8 mmol), and tetra-n-butylammonium iodide (2 g) in tetrahydrofuran (100 mL) was heated to reflux for 20 hours. The mixture was cooled, and poured into water (400 mL). This was extracted with methylene chloride (2 ×400 mL), and the extracts were combined, dried over anhydrous magnesium sulfate, filtered and evaporated. The residual oil was purified by elution through a short plug of silica gel with ethyl acetate, and evaporation afforded ethyl 5-[4,5-bis(4-methoxyphenyl)-1H-imidazole-2-ylthio]pentanoate (14.4 g, 32.6 mmol, 98%) as a waxy, low-melting solid.
