Transformations of CO2 into carboxylic acids are ideal reactions due to the widespread application of carboxylic acid compounds in the chemical and pharmaceutical industries. In general, direct C-H bond or C-X (X= halides) functionalization would allow 'unfunctionalized' molecules to be converted into synthetic intermediates and perhaps more importantly, an existing functionality could be exploited or suppressed selectively, during the assembly of molecular complexity. The approach could also allow complex molecules, especially pharmaceuticals, to be prepared in fewer steps. This proposal is concerned with N-heterocyclic carbenes (NHCs) catalysed C–H/ C-X bond functionalization of organic molecules followed by the insertion of CO2 to afford carboxylic acids. I intend to develop general site-selective strategy that takes place under mild conditions. The catalysts developed will be used to functionalize a range of organic motifs including 'functionally challenging' molecules found in natural products and complex pharmaceutical agents.