Rigid components from Schiff bases

Note Work in a fume hood wherever possible and exercise due caution when handling sodium hydride. 

Under an inert atmosphere, prepare a suspension of sodium hydride (0.96 g, 20 mmol [50 per cent in mineral oil]) in dry THF (50 mL) in a 250 mL twonecked round-bottomed flask fitted with a reflux condenser and pressure equalized addition funnel. Stir for 30 min under an inert atmosphere. Slowly add a solution of 8-hydroxyquinoline (2.90 g, 20 mmol) in dry THF (50 mL) to this through the addition funnel. Make up a solution of triethylene glycol ditosylate, 2, (4.60 g, 10 mmol) in dry THF (50 mL), ensuring that no solids remain (filter if necessary) or the addition funnel may become blocked. Once the effervescence subsides following the formation of the sodium 8-hydroxyquinolinate salt, add the ditosylate solution and reflux for 24 h. After 24 h, allow the solution to cool to room temperature, filter off the precipitated sodium tosylate and remove the THF by rotary evaporation. Dissolve the residue in dichloromethane (30 mL) and wash with distilled water (3 x 30 mL). Dry the organic phase over anhydrous sodium sulphate, filter and remove dichloromethane by rotary evaporation to give the crude product, l,9-bis(8-quinolinyloxy)-3,6-dioxanonane (4) as a pale brown oil. Further purification may be afforded by column chromatography (silica, elute with acetone/dichloromethane). 

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