Nano-organocatalytic Michael reactions promoted by Chiral Carbon Dots

Chiral Carbon Dots (CCDs) are carbon nanoparticles easily synthetized from small and readily available organic molecules, with an active surface which retains the molecular features of the starting materials, including chiral properites.1 Recent studies demonstrate the low toxicity of this promising and bio- compatible materials, underling widespread applications in chemistry.2 High solubility in water, in addition to others organic solvents, together with the possibility of an efficient functionalization of the active surface allow the use of CCD as nano-organocatalyst in several organic reactions.3 In fact, the presence of characteristic and tunable functional groups on the surface, paired with the chiral information, could lead to a strong interaction with substrates, aiming to promote stereoselective transformations. Herein, an innovative synthetic approach to activate Michael donors is reported, exploring the potentiality of CCDs as green catalysts with two different types of activations. The reaction between 3-Methyl-1- phenyl-2-pyrazoline-5-one (1) and β-Nitrostyrene (2) was investigated relying on a non-covalent activation by L-phenylalanine-derived CCDs, while L-proline-functionalised CCDs were prepared to promote the Michael reaction between cyclohexanone (4) and 2. The desired products were isolated with high yields and moderate to good stereoselectivity under operationally simple and sustainable conditions, allowing for the efficient recovering and recycle of the nano-catalysts.