Studies on Lewis‐Acid Induced Reactions of 8‐Methoxy[2.2]metacyclophanes: A New Synthetic Route to Alkylated Pyrenes

Anti ‐8‐methoxy[2.2]metacyclophanes (MCPs) 5   a – b were obtained via pyrolysis of the corresponding syn ‐thiatetraoxide cyclophanes 4   a – b . Coupling reactions of 4‐ tert ‐butyl‐1‐methoxy‐2,6‐bis(mercaptomethyl)benzenes 1   a – b and 1,5‐bis(chloro‐methyl)‐2,4‐dimethylbenzene 2 under high dilution conditions afforded only the syn ‐conformers of 9‐methoxy‐2,11‐dithia[3.3]metacyclophanes 3   a – b , which with m ‐CPBA formed the corresponding syn ‐tetraoxides 4   a – b . Lewis acid (TICl 4 /AlCl 3 ‐MeNO 2 ) or iodine‐catalyzed reactions of 5   b under various conditions led to transannular cyclization to afford tetrahydropyrene 6   b and pyrene derivative 7   b and/or de‐ tert ‐butylated 6   a . Iodine‐catalyzed reaction of 5   a afforded tetrahydropyrene 6   a . These findings suggest the potential for a new route to alkylated pyrenes via strained and alkylated metacyclophanes. Density functional theory (DFT) studies were carried out to investigate the conformational characteristics of 3–5 .