Synthesis of Tetrahydro‑1<i>H</i>‑indeno[1,2‑<i>b</i>]pyridine via Cascade Cyclization and Friedel–Crafts Reaction

A convenient protocol has been established for the synthesis of 1-tosyl-2,3,4,5-tetrahydro-1H-indeno­[1,2-b]­pyridine via cascade cyclization and Friedel–Crafts reaction of 4-methyl-N-(pent-4-yn-1-yl)­benzenesulfonamides and aldehydes in good yields. The methodology has been used for the total synthesis of the antidepressant agent (±)-5-phenyl-2,3,4,4a,5,9b-hexahydro-1H-indeno­[1,2-b]­pyridine.