A convenient stereoselective method for synthesis of β-lactams under microwave irradiation with [BmIm]OH as a reusable ionic liquid.

: A promoted synthetic protocol for the β-lactams synthesis in the presence of [BmIm]OH as a basic reagent under microwave irradiation [M.W.I.] is described. The reaction was highly diastereoselective. In all cases, this protocol provided trans-β-lactams as major isomers, and β-lactams were obtained with good yields. Further, the effect of the order of addition of the reagents was particularly investigated; we found that this order is very important. The best results are obtained when the imine is added gradually. This work shows that [BmIm]OH is an advantageous recyclable basic reagent. A qualitative molecular orbital diagram is illustrated to interpret the observed diastereoselectivity.