Structure and Photochemistry of 18-Diazo-1,4,7,10,13,16-hexaoxacyclononadeca-17,19-dione and Its Sodium and Potassium Complexes.Control of the Ground-State Conformation of 2-Diazo-l,3-dicarbonyl Fragment via Host-Guest Complexation

摘要

The macrocyclic 18-diazo-l,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 is K_(K~+) = 229 +- 25 M~(-1)) and sodium ions (3,K_(Na~+) = 84.2 +- 7.9 M~(-1) in methanol).According to B3LYP/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 crystal structure analysis showed that the potassium complex (2) has the same Z,Z arrangement,while the 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 a,a'-dicarbonylcarbene into the O-H bond of the solvent.The triplet-sensitized photolysis of diazomalonates 1-3 produces 2,4-dioxo-19-crown-6 (6),which is apparently formed via the triplet state of the intervening carbene.