In the past years,trifluoroacetylation has been widely used for protecting func-tional groups.For example,trifluoroacetyl can act as an effective blocking group ofhydroxyl and amino substituents in the reactions of a ...In the past years,trifluoroacetylation has been widely used for protecting func-tional groups.For example,trifluoroacetyl can act as an effective blocking group ofhydroxyl and amino substituents in the reactions of a 1-halo-2-hydroxyl-3-amino sugarwith cholesterol or cyclodecanol.Furthermore,the conversion of the basic aminogroup to less basic amido group by trifluoroacetylation provides a good chromatographyseparation method of amines,e.g.cis-,trans-1,2-diaminocyclohexane can be separatedcompletely,via trifluoroacetylation by GLC technique.展开更多
Our previous research showed that aliphatic amines were put in order of high reactivity as “ethylamine > ammonia > t-butylamine > diethylamine” on the aromatic nucleophilic substitution of 1-dimetylamino-2,...Our previous research showed that aliphatic amines were put in order of high reactivity as “ethylamine > ammonia > t-butylamine > diethylamine” on the aromatic nucleophilic substitution of 1-dimetylamino-2,4-bis(trifluoroacetyl)-naphthalene 1 in acetonitrile. The DFT calculation study (B3LYP/6-31G* with solvation model) for the reactions of 1 with above four amines rationally explained the difference of each amines reactivity based on the energies of their Meisenheimer complexes 3 which are assumed to formed as the reaction intermediates in the course of the reaction giving the corresponding N-N exchange products 2. Intramolecular hydrogen bond between amino proton in 1-amino group and carbonyl oxygen in 2-trifluoroacetyl group stabilizes Meisenheimer complexes 3 effectively, and accelerates the substitution reaction from 1 to 2. Our calculation results also predicted that the above order of amines is also true if less polar toluene is used as a solvent instead of acetonitrile even though more enhanced conditions are required.展开更多
文摘In the past years,trifluoroacetylation has been widely used for protecting func-tional groups.For example,trifluoroacetyl can act as an effective blocking group ofhydroxyl and amino substituents in the reactions of a 1-halo-2-hydroxyl-3-amino sugarwith cholesterol or cyclodecanol.Furthermore,the conversion of the basic aminogroup to less basic amido group by trifluoroacetylation provides a good chromatographyseparation method of amines,e.g.cis-,trans-1,2-diaminocyclohexane can be separatedcompletely,via trifluoroacetylation by GLC technique.
文摘Our previous research showed that aliphatic amines were put in order of high reactivity as “ethylamine > ammonia > t-butylamine > diethylamine” on the aromatic nucleophilic substitution of 1-dimetylamino-2,4-bis(trifluoroacetyl)-naphthalene 1 in acetonitrile. The DFT calculation study (B3LYP/6-31G* with solvation model) for the reactions of 1 with above four amines rationally explained the difference of each amines reactivity based on the energies of their Meisenheimer complexes 3 which are assumed to formed as the reaction intermediates in the course of the reaction giving the corresponding N-N exchange products 2. Intramolecular hydrogen bond between amino proton in 1-amino group and carbonyl oxygen in 2-trifluoroacetyl group stabilizes Meisenheimer complexes 3 effectively, and accelerates the substitution reaction from 1 to 2. Our calculation results also predicted that the above order of amines is also true if less polar toluene is used as a solvent instead of acetonitrile even though more enhanced conditions are required.
