Synthesis
A solution of 5,6-dimethoxy-indanone (19 g, 0.10 mol) in methanol (8 mL) is stirred under inert
atmosphere at room temperature. Slowly add NaOH flakes
(12.8 g, 0.32 mol) followed by N-benzyl-piperidine-4-carboxaldehyde (20.2 g, 0.10 mol) to the reaction mixture. The
mixture was stirred at room temperature for 3 h and progress
of the reaction was monitored by TLC (hexane:ethyl acetate;
1:1). Once the reaction is complete, the solid formed was
filtered, washed with 5 % acetic acid and then with methanol
and dried. The obtained solid (34 g) was taken into a round
bottom flask and refluxed with DMF (50 mL). Gradually cooled
to room temperature and stirred for 2 h, filtered the solid
formed, wash with chilled methanol to afford a pale yellow
crystalline solid 1-Benzyl-4-(5,6-dimethoxy-1-oxoindan-2-ylindenemethyl)piperidine (32.0 g, 84 %); m.p.: 175-177 °C.
References
[1] Patent: US2009/253746, 2009, A1. Location in patent: Page/Page column 3
[2] Patent: EP1911745, 2008, A1. Location in patent: Page/Page column 11-12
[3] Patent: EP1911745, 2008, A1. Location in patent: Page/Page column 10
[4] Patent: EP1911745, 2008, A1. Location in patent: Page/Page column 14
[5] Organic Process Research and Development, 2008, vol. 12, # 4, p. 731 - 735
