Sterically crowded 1,4-diiodobenzene as a precursor to difunctional hypervalent iodine compounds

摘要

A bulky 1,4-di-iodobenzene having four adjacent para-tBu-C6H4 group (Ar′) substituents (1) was used to prepare the di-hypervalent iodine compound 1,4-I(OAc)22-2,3,5,6-Ar′4-C6 (2). Despite the steric encumbrance of the iodine center by the flanking aryl substituents, compound 2 undergoes ready cyclization under mild conditions (excess CF3COOH at 55 °C, 30 min) to afford a dicyclic di-iodonium di-triflate salt 3. The single crystal structures of compounds 2 and 3 were examined and compared to the formerly characterized precursor 1. The para-tert-butyl groups on these compounds also render the compounds more soluble than multifunctional hypervalent iodine (HVI) compounds. HVI compounds having multiple iodine(iii) centers are increasingly of interest for applications as recyclable reagents, materials precursors, and as Lewis acids.