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

Abstract

203-208Facile 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% H2SO4, H3PO4 and AlCl3/CH3NO2 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 AlCl3 catalyst resulted in varying amounts of side products. The starting and final products were characterized by elemental analysis and IR, 1H NMR and MS data