Synthesis of some macrocycles/bicycles from bis(o-formylphenyl) selenide: X-ray crystal structure of bis(o-formylphenyl) selenide and the first 28-membered selenium containing macrocyclic ligand

Bis(o-formylphenyl) selenide (7) was synthesized using the ortholithiation methodology. The reaction of o-lithiobenzaldehyde acetal (5) with Se(dtc)2 (dtc=diethyldithiacarbamate) afforded bis(o-formylphenyl) selenide acetal (6) in good yield. The key starting material 7 was isolated as pale yellow solid upon refluxing 6 with concentrated HCl. The structure of 7 was solved in the monoclinic space group P2/c with cell constants a=8.0170(6) Å, b=8.4514(6) Å and c=17.5289(12) Å, Z=4. The condensation of 7 with diethylenetriamine yielded the novel macrocyclic ligand [C36H38N6Se2] 8 via metal-free dimerization. Crystals of 8 are monoclinic, space group C2/c with a=18.732(3) Å, b=8.6515(10) Å, c=22.590(3) Å and Z=4. Hydrogenation of macrocycle 8 provided the corresponding saturated tetraazamacrocycle [C36H46N6Se2] (9), protonation of which with HBr afforded [C36H52N6Se2Br6·H2O] (10). The two novel cryptands [C54H54N8Se3] (12) and [C54H54N8Te3] (13) were prepared from the reaction of tris(2-aminoethyl)amine (tren) and the chalcogenides (7) and bis(o-formylphenyl) telluride (11) respectively using cesium ion as the template.