Benzenepropanoic acid → 2-(2-phenylethyl)-1H-benzimidazole

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Reaction Steps

A 100 mL flask fitted with a stir-bar and condenser was charged with 1,2-phenylenediamine (2.88 g, 26.6 mmol), hydrocinnamic acid (4.00 g, 26.6 mmol), and 4M HCl (40 mL). The resultant suspension was heated in a 130° C. bath 48 hr. The mixture was cooled, and the precipitate was filtered. The solid was suspended in H2O (70 mL), and the suspension was brought to pH 11 with 50% aqueous NaOH and stirred overnight. The pH was readjusted from 3 to 11 with 50% NaOH. The solid was filtered, pressed with rubber dam, and rinsed with H2O (2×10 mL). The material was dried to give 4.9 g of 67 as a white solid (83%). 1H NMR (60 MHz, CDCl3): δ 12.3 (s, 1H), 7.6-7.4 (m, 2H), 7.4-6.8 (m, 7H), 3.2 (s, 4H) ppm. HPLC analysis (15:10:75 H2O:A1:MeOH) showed a purity of greater than 99% with a retention time of 3.2 min.

Provenance & Evidence