Jitendra R. Harjani

Lewis acidic ionic liquids for the synthesis of electrophilic alkenes via the Knoevenagel condensation

1-Butyl-3-methylimidazolium chloroaluminate, [bmim]Cl·AlCl3, N=0.67 and 1-butylpyridinium chloroaluminate, [bpy]Cl·AlCl3, N=0.67 ionic liquids were found to work well as the Lewis acid catalyst and solvent in the Knoevenagel condensations of benzaldehyde and substituted benzaldehydes with diethyl malonate to give benzylidene malonates. The benzylidene malonates subsequently underwent Michael additions with diethyl malonate. The extent of Michael product formed during the reaction was found to vary with the Lewis acidity and the molar proportion of ionic liquid. The influence of Lewis acidity of the ionic liquid on the Knoevenagel and Michael products is demonstrated. In the case of 2-hydroxyarylaldehydes, the reactions led to the formation of 3-ethoxycarbonyl coumarins under ambient conditions.

Lipase-catalysed transesterification in ionic liquids and organic solvents: a comparative study

Abstract The lipase-catalysed transesterifications of 2-hydroxymethyl-1,4-benzodioxane in two different ionic liquids, 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim]PF 6 and 1-butyl-3-methylimidazolium tetrafluoroborate, [bmim]BF 4 and different organic solvents was studied. The hydrophobic and hydrophilic properties of ionic liquids and organic solvents do influence the lipase activity as illustrated from the results. The influence of the ionic liquid as an additive in an organic solvent on this reaction has been demonstrated. The enzymes in ionic liquids in combination can be recycled for several runs without substantial diminution in the lipase activity.

Lipase-catalysed polyester synthesis in 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid

1-Butyl-3-methylimidazolium hexafluorophosphate ionic liquid was employed as a reaction medium for lipase-catalysed aliphatic polyester synthesis. Lipase PS-C exhibited excellent catalysis in polycondensation of diethyl octane-1,8-dicarboxylate and 1,4-butanediol at room temperature and at 60°C. A relatively high molecular weight polymer was obtained at 60°C.

Fries rearrangement in ionic melts

Abstract 1-Butyl-3-methylimidazolium chloroaluminate, [BMIm] + Al 2 Cl 7 − , was used as a solvent as well as a Lewis acid catalyst in Fries rearrangement reactions of phenyl benzoates. The rate of consumption of phenyl benzoate obeyed first-order kinetics. Good yields and high selectivity are the features observed in this unconventional but interesting aprotic solvent.

TRANSPROTECTION OF SILYL ETHERS OF NUCLEOSIDES IN FeCl3 BASED IONIC LIQUIDS

Ionic liquid mediated deprotection of tert-butyldimethyl silyl (TBDMS) ethers derived from various primary and secondary alcohols have been studied and the reaction conditions optimized. Deprotection of the silyl ethers in FeCl3 based ionic liquids in presence of acetic anhydride yielded the acetate esters of the corresponding alcohols in good yields. The transprotection methodology was extended to the silyl ethers of nucleosides to yield the corresponding acetylated products.