Ionic Liquids (ILs) in Direct Reductive Amination (DRA): A Review and Studies on the One Pot DRA of Aldehydes in 1-Butyl-3-methylimidazolium tetrafluroborate (BMIMBF4 ) IL

Preliminary study in the Direct Reductive Amination (DRA) reaction of carbonyl compounds using green solvents i. e. Ionic Liquids as opposed to traditional solvents has been performed. Limitations (toxicity, cost, selectivity and addition of catalyst) of the traditional solvents led to interest on alternative green solvents. Thus, studies in the use of Ionic Liquids in the DRA of carbonyl compounds is emerging. Presented here is a review of ILs use in the DRA of aldehydes and ketones. The successes recorded, selectivity and recyclability have been highlighted in the review. Further, one pot DRA of various amines with aromatic aldehydes including stearically hindered aldehydes in 1-Butyl-3-methylimidazolium tetrafluroborate (BMIMBF4) IL is illustrated. The reactions proceeded selectively with excellent yield without the use of catalyst/protecting group. Trend in the selectivity of conversion revealed that Basic greater than Acidic and less/non Stearically hindered greater than Stearically hindered aldehydes. Importantly, the synthesis of amines through the DRA of aldehydes and amines (aliphatic and aromatic) with and without stearic hindrance was achieved.