Selective derivatisations of resorcarenes - 2. Multiple regioselective ring closure reactions

The condensation of the C-pentyl resorcarene 1 with long chain aliphatic diamines 3a-d and excess formaldehyde leads under high dilution conditions to tetrabenzoxazine derivatives 4a-d in which pairs of adjacent oxazine rings are connected by an aliphatic chain. Six new rings are formed per resorcarene molecule during this reaction in a regioselective way. For one example (4a) the chiral cleft-like structure with C₂ symmetry was proved by single crystal X-ray analysis. Hydrolysis of the oxazine rings gives the secondary amine derivatives 5a,b with C_2v symmetry in high yield.