Rao, Zenobia X; (2019) The application of 3D-printing in batch and flow chemistry for the synthesis of heterocycles. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The work described in this thesis focusses on 3D-printing as a novel technology and its use in both batch and flow chemistry. As such, fused deposition modelling and stereolithography printing were explored for their ability to affect organic synthesis. Initially, FDM printed column reactors for flow chemistry were developed and their scope in simple SNAr chemistry explored. This work was further expanded into the synthesis of quinoxalinones, wherein a two-step flow sequence using this SNAr step and an intramolecular acylal cyclisation step was able to generate the core structure in a single process from amino acids and environmentally benign solvents. The next phase of the project focussed on the development of devices for batch chemistry using SLA printing. A catalytic stirrer bead device that would improve the efficiency of batch reactions was developed. The initial formulation incorporated tosic acid and these stirrer bead devices were used in the synthesis of Hantzsch dihydropyridines. This formulation was then further improved so as to make it chemically inert and palladium(0) tetrakis(triphenylphosphine) containing devices were prepared. Their scope was explored through their use in Suzuki couplings under both thermal and microwave conditions. A third catalytic stirrer bead device containing yttrium triflate was also developed and its use in the protection of carbonyl groups in aldehydes with thiols was investigated using microwave conditions. In the last phase of the project, an SLA printed circular disc reactor was designed and fabricated using this new inert formulation. Its use in flow photochemistry has been explored shortly though C-H functionalisation chemistry and its limits have been explored. Last of all, the decarboxylation reaction in a synthetic sequence for Praziquantel was studied. It was found that a flow photo-decarboxylation using these newly developed reactors would be sufficient to carry out this key step in the synthetic sequence. The thesis closes with a description of the experimental conditions and full detail of the compounds produced in this thesis.

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