Tandem hydroformylation/aldol condensation reactions: Synthesis of unsaturated ketones from olefins

Platinum-catalysed tandem hydroformylation/ aldol condensation reaction of vinyl aromatics and ketones toward the corresponding alpha, beta-unsaturated ketones were performed under syngas atmosphere in the presence of acid co-catalysts. The in situ generated catalysts modified with various ligands proved to be efficient under applied conditions. The presence of acids promotes side reactions like hydrogenation of the alkene substrate and that of the aldehyde to the corresponding alkane and alcohol, respectively. Interestingly, the hydrogenation of the condensed products is not preferred, only trace amounts of saturated products can be detected by GC-MS. In general, moderate yields can be achieved with several ketones using styrene and alpha-methylstyrene as substrate in hydroformylation reaction. Linear aldehydes proved to be more active in aldol condensation step, furthermore, aromatic and cyclic ketones are also feasible coupling partners to generate the corresponding unsaturated ketones. Contrary to the preceding literature, ketones possessing alpha-methylene group(s) showed exclusive preference for methylene functionalization in the aldol condensation reaction. (C) 2018 Elsevier B.V. All rights reserved.