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Free keywords:
DIELS-ALDER REACTIONS; PERCHLORATE DIETHYL-ETHER; LITHIUM PERCHLORATE; ELECTROSTATIC CATALYSIS; AQUEOUS-SOLUTION; WATER; REARRANGEMENT; DIENOPHILES; CANTHARIDIN; CHEMISTRY
Abstract:
Ionic reactions with polarized transition states are favored by the solvent system LiClO4/Et2O (3-5M). This is demonstrated by (hetero)Diels-Alder reactions and by the sigmatropic rearrangement of allyl vinyl ethers in this medium. The former react even faster and with higher endo selectivity than in water; the latter are not [3,3] but [1,3] sigmatropic rearrangements, which yield aldehydes. An important advantage of the LiClO4/Et2O system is it that may also be used for acceleration of reactions sensitive to hydrolysis.
