Phosphonium tosylates as solvents for the Diels–Alder reaction

Environmentally Benign Solvent Systems: Toward a Greener [4+2] Cycloaddition Process

“…92 The yields and selectivities for these reactions are dependent upon both the substrates involved and the ionic liquid used, with methyl acrylate and methylvinyl ketone generally showing excellent selectivity for 1,4-products (1,4:1,3, >99:1). As a dienophile, acrylonitrile leads to poorer selectivity (1,4:1,3, 2.2:1 -3.2:1).…”

Ionic Liquids: Synthesis and Characterisation of Triphenylphosphonium Tosylates

“…Ͻ 100°C), whereas a considerably higher value has been obtained during this study. It is noted in passing, however, that 1, 3 and 5 have been used at temperature as low as 80°C, 40°C and 60°C [13] respectively although the melting points obtained for the pure phases are ca. 140°C, 133°C and 130°C, respectively.…”

“…Diels-Alder reactions of isoprene with methyl acrylate, but-3-en-2-one and acrylonitrile have also been performed in phosphonium tosylates, including 1, 3, 5 and 9. [13] The results indicate that product selectivity varies with cation substituent and also that the solvents are more suitable for the reactions of oxygen-containing dienophiles than for nitrogenous ones, showing high regioselectivity. Phosphonium salts including 1 and 9 have also been reported to be good co-catalysts for the Baylis-Hillman reac-tion with the results showing that neither modification of the cation substituents nor a change in the anion has a major effect on the yield.…”

“…On cooling, the salts crystallise out and trap the catalyst thereby enabling easy separation of liquid products. For example, in the hydroformylation, [12] Diels-Alder [13] and hydrogenation [15] reactions mentioned above, product separation involved filtration or decantation of the liquid organic product. The catalyst system or ionic solvent was subsequently reusable.…”

Phosphonium tosylates as solvents for the Diels–Alder reaction with 1,3–cyclopentadiene

“…7 The reaction proceeds with high regioselectivity, even without the use of Lewis acids as catalysts. The reaction temperatures are moderate and the solvents can be reused.…”