DIELS ALDER REACTIONS IN ROOM TEMPERATURE MOLTEN SALTS

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Ambient temperature chloroaluminate molten salts, AlCl/3:MCl, where Mcl is either 1-ethyl-3-methyl-1H-imidazolium chloride (EMIC) or N-1- butylpyridinium chloride (BPC), have never been used as solvents/catalysts for the synthetically important Diels-Alder reaction. This is unfortunate because one might expect to observe unusual and interesting [4pi + 2pi]- cycloaddition reactions in ionic liquids. The composition of molten salts can be easily varied from basic (EMIC or BPC in excess) to acidic (AlCl/3 in excess). This variable Lewis acidity of the molten salts is unique and should have a profound effect on Diels-Alder reactions. Furthermore, protons in ambient temperature molten salts function like Brphisted superacids with Hammett acidity functions, H/0, ranging from -12.6 (1.04: 1.0 mol ration AlCl/3-EMIC) to -18 (2: 1 mol ration AlCl/3-EMIC). This "doubly acidic" medium should significantly influence Diels-Alder reactions which is known to be affected by Lewis and Brphisted catalyst. These acid catalysts not only greatly accelerate the rate of reaction but also enhance diastereo-and regioselectivity. The proposed research involves a systematic investigation into the suitability of ambient temperature molten salts as solvents/catalysts for Diels-Alder reactions. Specific items to be studied include: (1) to highlight the potential of ambient temperature molten salts as useful solvents for intra- and intermolecular Diels-Alder and related reactions; (2) to investigate the influence of the solvent's Lewis and Brphisted acidity on Diels-Alder reactions; (3) to compare the Lewis versus Brphisted effect of the solvent on the rate and stereochemistry of Diels-Alder reactions; (4) to identify and characterize the reaction products and intermediates resulting from various intra- and intermolecular Diels-Alder reactions in the molten salt medium; and (5) to investigate the potential of molten salts as solvents/catalyst for synthesizing a variety of natural products and physiologically active molecules via Diels-Alder reactions. Results from the proposed study should provide the scientific community with a rather significant new area for material synthesis.