Synthesis of indeno[1,2,3-ij]isoquinolines

Abstract

1-Methyl and 1-benzyl-1,2,3,10b-tetrahydro-5,6,8,9-tetramethoxyindeno[1,2,3-ij]isoquinoline have been synthesized from the corresponding 8-phenyl-3,4-dihydro-1(2H)isoquinolinones by treatment with POCl₃ under Vilsmeier conditions followed by borohydride reduction. The isoquinolinones were prepared in six steps from 2-(2,3,4-trimethoxyphenyl)-4,4-dimethyl-2-oxazoline. This sequence of reactions provides a new route to dihydro and tetrahydroindeno[1,2,3-ij]isoquinolines.