E-factor minimized protocols for the polystyryl-BEMP catalyzed conjugate additions of various nucleophiles to α,β-unsaturated carbonyl compounds

Efficient protocols for the addition of carbon-, sulphur-and nitrogen-nucleophiles to alpha,beta-unsaturated carbonyl compounds catalyzed by PS-BEMP have been reported. The adoption of solvent-free conditions (SolFC) was crucial for improving the efficiency of all the processes, while by using an organic reaction medium poor results were obtained. Addition reactions were performed by using equimolar amounts of reagents, and the products were isolated by simple filtration with the minimal amount of organic solvent. This approach allowed the E-factor, a measure of the waste of a reaction, to be minimized. Further waste minimization (95.7% compared to batch protocol) has been accomplished by defining a larger scale continuous-flow protocol operating under SolFC.