Rh-catalyzed selective synthesis of 1,5-dimethylhexahydro-1H-inden-4(2H)-one via hydroformylation of (R)-carvone

Abstract

This work reports domino hydroformylation, hydrogenation and intramolecular keto-aldol condensation reactions for the selective synthesis of 1,5-dimethylhexahydro-1H-inden-4(2H)-one obtained from (R)-carvone and dihydrocarvone under homogeneous hydroformylation condition. The synthesis of the desired product was achieved by using conventional rhodium/1,3-bis(diphenylphosphino)propane (Rh/dppp) catalyst and PPTS (pyridinium p-toluenesulfonate) as an acidic co-catalyst. The reaction conditions were optimized with respect to various reaction parameters like time, temperature, synthesis gas (CO/H2) pressure, solvents, catalyst and co-catalyst loading. The experimental results showed that less planner carbon backbone in dihydrocarvone increases the steric hindrance around the reaction site and responsible for the reactivity difference between (R)-carvone and dihydrocarvone.