Substituent and solvent effects on the Diels–Alder reactions of triazolinediones

Diels–Alder reactions of anthracene, 9-substituted anthracenes and 9,10-disubstituted anthracenes

“…Electron-donating solvents increase solvation of the dienophile that can in turn decrease the reaction rate. 9 Solvents that are electron accepting can, in some cases, increase the rate of reaction by stabilisation of the transition state, which can be regarded as being electron rich. 8,9 Aromatic solvents produce large increases in reactivity with dienophiles that are capable of very strong charge -transfer interactions, 6 while salt effects have been observed for reactions performed in water.…”

“…9 Solvents that are electron accepting can, in some cases, increase the rate of reaction by stabilisation of the transition state, which can be regarded as being electron rich. 8,9 Aromatic solvents produce large increases in reactivity with dienophiles that are capable of very strong charge -transfer interactions, 6 while salt effects have been observed for reactions performed in water. 10,11 However, in general, the influence of the solvent on the rate of reaction, independent of the system investigated, has been shown to be relatively small, rarely above a factor of ten.…”

Influence of the Solvent Polarity on the Stereoselectivity of the Uncatalyzed [4+2] Cycloaddition of Cyclopentadiene toN,N′-Fumaroyldi[(2R)-borane-10,2-sultam]

“…51%) or lower in H 2 O ( E T (30) 63.1 kcal/mol, 92% de instead of calc. 93%) 4 ). This may tentatively be explained by the influence of the excess of cyclopentadiene which slightly modifies the overall polarity of the solvent.…”

Ene-type adducts from the reaction of 4-phenyl-1,2,4-triazoline-3,5-dione with β-alkyl s-cis enones

“…7) and seemed to be an appropriate choice for the trapping experiments. 'A portion of this work appeared as a preliminary communication (1).…”