Clean, efficient syntheses of cyclotriveratrylene (CTV) and tris-(O-allyl)CTV in an ionic liquid

Cyclic cyclotriveratrylene (CTV) type supramolecular host compounds are tra ditionally synthesized under harsh dehydrating conditions and require the u se of large quantities of organic solvent in the reaction workup. We now re port both solvent-free and ionic liquid reaction media in efficient 'green' syntheses of CTVs under mild conditions. The ionic liquid tributylhexylamm onium bis(trifluoromethylsulfonyl)amide (N-6444 Imide) provides a safe, non -volatile reaction medium that is readily recycled. This methodology obviat es the need for the use of large quantities of organic solvent and strong d ehydrating acids yet provides pure crystalline product in high yields. Unli ke most traditional synthetic routes to these compounds extensive recrystal lisation or chromatographic steps are avoided and the molten salt reaction medium is readily recovered. Interestingly, condensation also occurs under ambient conditions on grinding of solid benzyl alcohol monomers with a suit able solid acid to afford the corresponding CTV. Ionic liquids have, as yet , been little explored as reaction media or solvents yet these offer signif icant advantages over volatile (and often toxic) organic solvents. Human ex posure to potentially harmful vapours is obviated and recycling of the ioni c liquid reaction medium significantly reduces waste generated. The procedu res described here serve to extend the use of ionic liquids as reaction med ia.