Kinetic and Mechanistic Studies of the Selective Hydrogenation of (E)‐Chalcones in Biomass‐Derived γ‐Valerolactone Catalyzed by Rh−PPh₃ Complexes

Abstract

γ‐Valerolactone as a renewable, polar aprotic solvent was evaluated in the selective hydrogenation of carbon‐carbon double bond of chalcones from both catalytic and mechanistic aspects. By using triphenylphosphine‐modified cationic rhodium catalyst systems reasonably high activities (TOFinitial∼1200 h−1) were achieved in the selective hydrogenation of (E)‐chalcone (CHL), as a common model substrate for α,β‐unsaturated ketones, to dihydrochalcone (DHC). Various derivatives of CHL, which were substituted on the styryl phenyl groups also showed exclusive selectivity for the hydrogenation of the C=C double bond. The optimal PPh3/Rh ratio was between 2.5 to 3, but higher ratios were advantageously also tolerated, which is beneficial for the process chemistry. The solvent GVL proved to stable enough under the reaction conditions for waste‐free recycling. Kinetic studies and NMR spectra from the analogous deuteration of chalcone by using the cationic Rh‐PPh3 system clearly show the olefin insertion as the rate‐determining step with definite irreversibility. By investigating the substituent effect on the phenyl ring of the styryl moiety of chalcone, a quasi‐linear correlation was found between the electronic parameters of the para‐substituents and the activity with electron donor groups being favorable for the reaction rate. In summary, an environmentally friendly and feasible method is presented for the production of valuable DHC intermediates in view of their pharmaceutical importance.

Valorization of the Exoskeletons of Crustaceans in Seafood Wastes to Chemicals in Renewable Solvents: A Catalytic and Mechanistic Study

“… , Among these chemicals, LA has been highlighted in the list of the “top 12 platform chemicals” by Werpy and Petersen . LA can widely be utilized in pesticides, pharmaceuticals, and cosmetics industries, and its esters can be considered as gasoline boosters. , For its derivative GVL, several innovative applications have been demonstrated recently such as a fuel additive, , solvent for synthesis , and catalysis, − igniting and lighter fluid, , building block for ionic liquid synthesis, etc.…”