A Fast Organometallic Route from p-Xylene, Mesitylene, and p-Diisopropylbenzene to Organoiron and Polycyclic Aromatic Cyclophanes, Capsules and Polymers

摘要

Para-xylene and mesitylene are among the most common and cheapest organic compounds. They form well-known robust sandwich complexes of the type [Fe(η~5-C_5H_5)(η~6-arene)]~+, by high-yield, large-scale reactions with ferrocene in the presence of aluminum chloride. Herein we report than these sandwich complexes and the p-diisopropylbenzene iron complex lead to new cyclophanes, organoiron cyclophanes, polyring derivatives, capsules, and polymers in two steps (three steps for the iron-free compounds). The electron-withdrawing character of the cationic 12-electron group FeCp~+ lowers the pK_a value of polymethylaromatics from 43 to 28 in DMSO, and the subsequent convenient deprotonation reaction can be exploited for facile and multiple C-C bond formation under ambient conditions. For instance, FeCp~-induced triallylation of toluene can be followed by ring-closing metathesis (RCM) to give a derivative containing a five-membered ring in 5 min at room temperature using the Grubbs metathesis catalyst [Ru-(PCy_3)_2Cl_2(=CHPh)], 1. On the other hand, dimerization of the iron complex by cross metathesis (CM) under these conditions does not occur, even after several days (Scheme 1).