Final Report Summary - HYDROACYLATION (Rhodium-catalyzed alkene and alkyne hydroacylation)
The hydroacylation reaction (HA) is a potentially powerful transformation in organic synthesis. The transformation of an aldehyde and an unsaturated hydrocarbon into a ketone involves C-H activation with C-C bond formation under atom-economical conditions. The main limitation of this reaction is the possible decarbonylation of one of the reaction intermediates. The most common catalysts for these processes are rhodium diphosphine complexes. The research proposal aimed the control of the undesirable decarbonylation pathway achiving by both attenuating decarbonylation and promoting the (rate limiting) reductive elimination step of the final product. The previous works in the host group demonstrated that hemilable ligands attenuate the decarbonylation and also complexes bearing small bite angle accelerated the main reaction.
Combining these two antecedents, we have synthesized a new family of rhodium complexes containing hemilabile small bite-angle diphosphine ligands (4th generation Weller-Willis catalyst). The new rhodium complexes were excellent catalyst for the intermolecular hydroacylation of a wide variety of inactivated alkene with β-substituted aldehydes. They were remarkably resistant to decarbonylation, allowing substrate recharged without loss in conversion. A detailed mechanistic study (rate, order and labelling studies) allowed us to understand the reaction mechanism and the reasons behind the high activity and selectivity of these catalysts.
The most used diphosphine ligands were changed by the novel NHCP ligand, both can show small bite angle when they are coordinated to the metal centre. The novel complexes showed to be active and selective for the intermolecular hydroacylation of alkynes with β-substituted aldehydes. Until the date and according to our knowledge there is any study of metal-mediated catalysed reactions employing this class of NHCP complexes.
Combining these two antecedents, we have synthesized a new family of rhodium complexes containing hemilabile small bite-angle diphosphine ligands (4th generation Weller-Willis catalyst). The new rhodium complexes were excellent catalyst for the intermolecular hydroacylation of a wide variety of inactivated alkene with β-substituted aldehydes. They were remarkably resistant to decarbonylation, allowing substrate recharged without loss in conversion. A detailed mechanistic study (rate, order and labelling studies) allowed us to understand the reaction mechanism and the reasons behind the high activity and selectivity of these catalysts.
The most used diphosphine ligands were changed by the novel NHCP ligand, both can show small bite angle when they are coordinated to the metal centre. The novel complexes showed to be active and selective for the intermolecular hydroacylation of alkynes with β-substituted aldehydes. Until the date and according to our knowledge there is any study of metal-mediated catalysed reactions employing this class of NHCP complexes.
