Catalysis with inorganic cations .7. The catalytic process of the Diels-Alder reaction with magnesium perchlorate in CH2Cl2: Kinetic investigation and spectroscopic detection of the complexed intermediate.

The 2-arylidene-malonic acid dimethyl ester is a dienophile suitable to be coordinated by Mg(II). The formation of the dienophile/cation complex in a ratio 2:1 in a non-coordinating solvent has been demonstrated by NMR spectroscopy. Kinetic determinations performed in dichloromethane evidenced the high reactivity of the system. The high affinity for Mg(II) of the reacting dienophile allows the reaction to be performed under catalytic conditions, whose single steps have been clarified by both spectroscopic and kinetic methods. (C) 1997 Elsevier Science Ltd.