Synthesis, Conformational Properties and DFT Computational Studies of [3]Metacyclo[3](1,3)pyrenophanes

Two new 6,17‐di‐ tert ‐butyl‐[3]metacyclo[3](1,3)‐pyrenophane‐2,11‐diones 8 a – b were synthesized by the coupling reaction of 1,3‐bis(bromomethyl)‐7‐ tert ‐butylpyrene 5 with the corresponding TosMIC‐adducts 7 a – b in CH 2 Cl 2 and water under phase‐transfer conditions, followed by acid treatment. Wolff–Kishner reduction of 8 a – b afforded in good yields the corresponding 6,17‐di‐ tert ‐butyl‐[3]metacyclo[3](1,3)‐pyrenophanes 9 a – b . The spectroscopic data of both 8 a and 8 b show that they adopt anti ‐conformations. In contrast, both pyrenophanes 9 a and 9 b adopt syn ‐conformations. Variable‐temperature 1 H NMR studies were carried out to determine the conformational behavior of the pyrenophanes. A single crystal X‐ray structure of 8 a shows that it also has an anti ‐conformation in the solid state. Density functional theory (DFT) computations of 8 a – b and 9 a – b were used to determine their energy‐minimized structures and the total energies of their different conformers.