Potassium Iodide → 6-iodo-3,4-dihydronaphthalen-1(2H)-one

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Reaction Steps

A mixture of N-(5-oxo-5,6,7,8-tetrahydronaphthalen-2-yl)-acetamide 2.5 grams (12.3 mmole) in 20 mL 20% sulfuric acid was heated at 90° for 45 minutes. The solution was allowed to cool to room temperature whereupon 6-amino-3,4-dihydro-2H-naphthalen-1-one sulfate (not shown) precipitated as a solid mass. To this solid was added 20 mL water and 20 mL glacial acetic acid. The resulting solution was stirred in an ice bath and a solution of 1.72 grams (25 mmoles) sodium nitrite in 15 mL water was added dropwise over 0.5 hour. The reaction mixture was slowly poured into a well stirred solution of 8 grams (48 mmoles) potassium iodide in 80 mL water. The mixture was extracted with 200 mL ethyl ether, and the organic phase was washed with water, then saturated sodium hydrogen sulfite, then with saturated sodium chloride. The organic phase was dried (magnesium sulfate) and concentrated under reduced pressure. The residue was subjected to low pressure column chromatography over silica gel 230-400 mesh eluting with 5% ethyl acetate in hexane. 6-Iodo-3,4-dihydro-2H-naphthalen-1-one was obtained as a white solid, 3.12 grams (94%), m.p. 77-78°.

Provenance & Evidence