Organic Synthesis in chiral melts and solid mixtures

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Most organic syntheses are performed in solution to ensure rapid conversion and good heat transfer. However, the use of deep eutectic melt mixtures as reaction media has advantages for some applications, such as very high substrate concentration and ease of performance. We have applied low melting mixtures of starting materials and catalysts for the conversion of carbohydrates and the synthesis of bioactive heterocycles. We now aim to expand the scope of melt mixture reactions to asymmetric synthesis. One component of the melt acts as chiral organocatalyst or chiral base and thereby controls the stereochemical outcome of the reaction. Amino acids and cinchona alkaloids are envisaged for this purpose. Alternatively a chiral component of the melt serves as starting material and is converted into chiral reaction products under melt conditions. The project should lead to efficient, practically simple and environmentally benign syntheses of complex chiral molecules from simple precursors. Not all mixtures of starting materials and catalyst compounds form deep eutectics. In particular biopolymers are difficult to dissolve in melts in larger quantities. We therefore investigate the mechanochemical conversion of bulk natural products in the solid state and the presence of reagents, catalysts or scavenger compounds into higher value fine chemicals. The conversion in the solid state overcomes incompatibilities in solubility and may provide different selectivites and product distributions.The expertise of both groups participating in the proposed research is ideally complementary: The Baskaran group (IIT Madras) has ample experience in the synthesis of complex natural products, in particular heterocycles and carbohydrates. The expertise of the König group (UR) is in the area of physical-organic chemistry and new reaction media. By the exchange of graduates students and postdocs new protocols for organic synthesis, including enantioselective transformations, without solvents will be established and the reaction mechanisms and media investigated.