Collect. Czech. Chem. Commun. 1999, 64, 527-532

Synthesis of 1,1,5,6-Tetramethyl- and 7-Isopropyl-1,1-dimethyl-1,2,3,4-tetrahydronaphthalene

Ramchandra Bhimrao Mane*, Abhijit Jaysingrao Kadam and Rajashree Sandeep Salunkhe

Department of Chemistry, Shivaji University, Kolhapur-416004, India


4-(2,3-Dimethylphenyl)butanoic acid (4) was treated with excess of methyllithium to yield 5-(2,3-dimethylphenyl)-2-methylpentan-2-ol (6) which was cyclodehydrated using Dowex 50W-X8 resin, trifluoroacetic acid or polyphosphoric acid (PPA) to furnish 1,1,5,6-tetramethyl-1,2,3,4-tetrahydronaphthalene (1). The acid 4 was cyclized with PPA to furnish 5,6-dimethyl-3,4-dihydronaphthalen-1(2H)-one (5) which was converted into 1 by reaction with dimethylzinc and titanium tetrachloride. 4-(4-Isopropylphenyl)butanoic acid (7) on esterification followed by Grignard reaction with methylmagnesium iodide furnished 5-(4-isopropylphenyl)-2-methylpentan-2-ol (9), which was cyclodehydrated as above to yield 7-isopropyl-1,1-dimethyl-1,2,3,4-tetrahydronaphthalene (2).

Keywords: 1,2,3,4-Tetrahydronaphthalenes; Friedel-Crafts reaction; Alkylation; Cyclization; Sesquiterpenoids.