Abstract (PDF) Graphical Abstract: In this work, the stereospecific synthesis of optically active cis β-lactams under diverse microwave-induced conditions using diverse solvents was reported. The effects of low tanδ values of the solvents are found to be more crucial than solvents with high dipole moments and dielectric constants. The results indicated that for the synthesis of β-lactams solvents with low tanδ and high dipole moment and high dielectric constant are necessary. Best of the knowledge this is the first report that examined the importance of tanδ values of the solvents in β-lactams synthesis.