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45.19.1.1.1.5.1 Variation 1: Friedel–Crafts Acylation

DOI: 10.1055/sos-SD-045-00684

Toyota, S.; Iwanaga, T.Science of Synthesis, (201045764.

3,4-Dihydronaphthalen-1(2H)-one (1-tetralone) (78, R1=H) is a key compound of the conventional synthetic methods for the synthesis of substituted naphthalenes. This compound is usually prepared by intramolecular FriedelCrafts acylation of 4-phenylbutanoic acid (77, R1=H) (Scheme 24).[‌65‌,‌66‌] In the classical synthesis, 4-phenylbutanoic acid (77, R1=H) is directly cyclized by treatment with phosphorus pentoxide[‌67‌] or sulfuric acid,[‌68‌] or its acid chloride is cyclized in the presence of aluminum trichloride[‌69‌] or tin(IV) chloride.[‌70‌] 3,4-Dihydronaphthalen-1(2H)-one is also synthesized by aluminum trichloride catalyzed cyclization of benzene with γ-butyrolactone (79, R1=H) in a one-pot reaction (Scheme 24).[‌70‌] The yields of these cyclization reactions are generally high. The above reactions require either a stoichiometric or excess amount of strong or Lewis acids. To reduce the waste, environmentally friendly reactions have been developed, for example using mild Lewis acids or polymer-supported strong acids.[‌71‌‌73‌] Thus prepared, tetralones can be converted into various naphthalenes by various methods (see Section 45.19.1.1.3.2).

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