Selective derivatization of resorcarenes.: 3.: C2-symmetrical and transcavity bridged bis-benzoxazines derived from C2ν-symmetrical tetratosylates

The regioselective condensation of resorcarene tetratosylates 3/4 with formaldehyde and various primary amines readily gives bis-benzoxazines 5/6 in 65-86% yield. The chiral, C-2-symmetrical structure of these compounds has been-proved by NMR-spectroscopy and single-crystal X-ray analysis. Bis-benzoxazines 5f and 5i assume in the crystalline state a boat conformation in which-the two resorcinol rings bearing the oxazine fragments are nearly parallel. The tosylated resorcinol units are horizontally arranged in a propeller-like fashion, and two intramolecular hydrogen bands are formed between the phenolic hydroxy groups and the oxygens of the neighboring sulfonyl fragments. Molecular mechanics calculations suggest that the regioselective formation of the C-2-isomer is caused by the repulsion between the substituents or the unpaired electrons at the nitrogen atoms of the two benzoxazine rings and by slightly better geometrical conditions for intramolecular S=O ... H-O hydrogen bonding in comparison with the meso-isomer. The aminomethylation of tetratosylate 3 with appropriate diamines leads to the first examples of 1,3-bridged derivatives of resorcarenes. Chiral (C-2-symmetrical) or meso-(C-s-symmetrical) compounds can be obtained depending on the length of the bridging chain. In the case of 1,3-diaminopropane a 1,3-diazacyclohexane (hexahydropyrimidine) bridge is formed by additional condensation with formaldehyde.