| Title
| - Structure and Photochemistry of18-Diazo-1,4,7,10,13,16-hexaoxacyclononadeca-17,19-dione and ItsSodium and Potassium Complexes. Control of the Ground-StateConformation of 2-Diazo-1,3-dicarbonyl Fragment via Host−GuestComplexation
|
| Abstract
| - The macrocyclic 18-diazo-1,4,7,10,13,16-hexaoxacyclononadeca-17,19-dione (3-diazo-2,4-dioxo-19-crown-6, 1) readily forms complexes with potassium (2, stability constant in methanol isKK+ = 229 ± 25 M-1) and sodium ions (3, KNa+ = 84.2 ± 7.9 M-1 in methanol). According toB3LYP/6-31G+(d,p) calculations and temperature-dependent 1H NMR spectroscopy, the predominant conformation of 1 has a Z,Z arrangement of the diazo and carbonyl groups. The X-ray crystalstructure analysis showed that the potassium complex (2) has the same Z,Z arrangement, whilethe sodium analogue (2) exists in conformation with Z,E geometry of the diazodicarbonyl moiety.Direct 254 nm photolysis of diazo compounds 1−3 in methanol results in the formation of 3-methoxy-2,4-dioxo-19-crown-6 (5), the product of the insertion of corresponding α,α‘-dicarbonylcarbene intothe O−H bond of the solvent. The triplet-sensitized photolysis of diazomalonates 1−3 produces2,4-dioxo-19-crown-6 (6), which is apparently formed via the triplet state of the intervening carbene.
|
