Modern Friedel-Crafts Chemistry. Part 30 1 Facile synthesis of isomeric tri- and tetramethyltetrahydrophenanthrenes via rearranged cycloalkylation of suitably methylated 1-(1- and 2-naphthyl)-3-pentanols

Facile methods for the synthesis of isomeric tri- and tetramethyl-tetrahydrophenanthrenes (11, 18, 21, and 27) have been accomplished through rearranged Friedel-Crafts cycloalkylation of naphthylpentanols 1-4, respectively. Thus, treatments with the mild 85% H 2 SO 4 , H 3 PO 4 and AlCl 3 /CH 3 NO 2 catalysts produced 1,1,2-trimethyl-1,2,3,4-tetrahydropenanthrene 11 from 2.2-dimethyl-5-(1-naphthyl)-3-pentanol 1, 3,4,4-trimethyl-1,2,3,4-tetrahydrophenanthrene 18 from 2,2-dimethyl-5-(2-naphthyl)-3-pentanol 2, 1,1,2,2-tetramethyl-1,2,3,4-tetrahydrophenanthrene 21 from 2,2,3-trimethyl-5-(1-naphthyl)-3-pentanl 3 and 3,3,4,4-tetramethyl-1,2,3,4-tetrahydropenanthrene 27 from 2,2,3-trimethyl-5-(2-naphthyl)-3-pentanol 4. Treatment with the strong AlCl 3 catalyst resulted in varying amounts of side products. The starting and final products were characterized by elemental analysis and IR, 1 H NMR and MS data.