Hydrochloric Acid → HCID 14555898, compound

Participants

Reaction Steps

To a RB flask equipped with magnetic stirring bar, condenser and N2 inlet line with bubbler was added methyl 5-formylnaphtho-[2,1-b]thiophene-2-carboxylate (7A, 9.75 g, 36 mmol), KOH (85%, Mallinckrodt Co., St. Louis, Mo. 63147, 18.0 g, 320 mmol), CH3OH (40 mL) and H2O (80 mL). The mixture was refluxed for 1.5 h, cooled and neutralized with 3 N HCl (500 mL). A yellow solid formed which was filtered and washed with H2O (3×300 mL) and dried in a vacuum oven overnight to give crude 5-formylnaphtho-[2,1-b]thiophene-2-carboxylic acid in quantitative yield. This material was then slurried with quinoline (Mallinckrodt, 60 mL) and cuprous oxide (MCB, 6.2 g, 43.3 mmol) and heated to 185° in an oil bath for 1 h. The reaction mixture was allowed to cool to RT then partitioned between Et2O (500 mL) and concentrated HCl (200 mL) containing saturated NH4Cl (100 mL). The layers were separated and the aqueous layer extracted with additional Et2O (500 mL). The Et2O layers were combined and washed in succession with 1 N HCl (300 mL), H2O (2×300 mL) and saturated NaCl solution (2×300 mL), dried (MgSO4), filtered and concentrated to give a light brown crude solid. After chromatography on SiO2 using CHCl3 /hexane as the eluting solvent and crystallization (CHCl3 /cyclohexane) there was obtained 4.98 g (65.2% yield) of naphtho[2,1-b]thiophene-5-carbaldehyde, mp 101°-102°, (C,H,S).

Provenance & Evidence