Synthesis, structure, and conformation of aza[1n]metacyclophanes.
N-Benzyl substituted aza[1n]metacyclophanes (n = 4, 6, 8, and 10) were prepared in overall 40% isolated yields via Pd-catalyzed aminations. Analyses of the reaction mixtures showed that aza[14]metacyclophane and the related polymer were the primary products ( approximately 60% overall yield); aza[1n]metacyclophanes up to n = 14 and linear oligomers with up to 20 nitrogen atoms (with at least three types of end groups) were detected. Macrocyclic structures for n = 4, 6, and 10 were confirmed by X-ray crystallography. 1,3-Alternate (D(2d)) and 1,3,5-alternate (S(6)) conformations in solution on NMR time scale at low temperatures were found for macrocycles with n = 4 and n = 6, respectively; the barrier for ring inversion was considerably lower for the larger macrocycle.
Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, USA.
Matthew
M
Vale
Maren
M
Pink
Suchada
S
Rajca
Andrzej
A
Rajca
D002384:Catalysis; D018360:Crystallography, X-Ray; D006841:Hydrocarbons, Aromatic / Q000138:chemical synthesis* / Q000737:chemistry; D008027:Light; D047028:Macrocyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D013058:Mass Spectrometry; D008958:Models, Molecular; D008968:Molecular Conformation; D010165:Palladium / Q000737:chemistry; D012542:Scattering, Radiation; D013237:Stereoisomerism
D006841:Hydrocarbons, Aromatic; D047028:Macrocyclic Compounds; D010165:Palladium