N-Alkylammonium Resorcinarene Picrate and Triflate Cavitands

The possibility of modifying resorcinarenes [1] either via nucleophilic aromatic substitutions at the position 2 on the aromatic ring or the phenol hydroxyl groups increases their potential for forming multifunctional compounds. Mannich [2] condensation is the most common and arguably the most important synthetic procedure in functionalizing resorcinarenes at the aromatic ring. Mannich condensation has been employed to connect pair of adjacent [3] and opposite [4] oxazine rings on resorcinarenes by aliphatic arms forming single and double handed baskets. Flexible ethylene diamine moieties have been used to connect two resorcinarenes in a 15% yield [5]. Openining of the oxazine ring by strong mineral acid (HX) results in the corresponding N-alkylammonium halide salts [6], which maintain the parent tetrabenzoxazine cone conformation. The anion exchange of the halide counter anions by silver picrate or silver triflate leads to the exchange of the halide to the corresponding picrate and triflate (Scheme 1). The X-Ray structures of the picrate (Fig. 1) and triflate shows more distorted cone conformations when compared to the corresponding chloride or bromide salts. In the case of triflate the anion exchage was not perfect and resulted in a 3:1 triflate:chloride salt.