A density functional theory investigation on bis(diethylamino)cyclopropenylidene catalyzed synthesis of 1, 4‐bifunctional compounds. (18th May 2021) - Shyam, Abhijit
Abstract: Bis(amino)cyclopropenylidenes (BACs) are the newly discovered umpolung catalysts with potential applications in the synthesis of numerous important organic moieties. A plausible mechanism for bis(diethylamino)cyclopropenylidene (Et‐BAC) catalysed synthesis of 1, 4‐diketones has been investigated using density functional theory (DFT). The proposed catalytic cycle initiates with the nucleophilic interaction of in situ generated Et‐BAC with p ‐methoxybenzaldehyde to form a zwitterionic intermediate, which on proton transfer reaction gives Breslow intermediate. Breslow intermediate then favours 1, 4‐umpolung addition reaction with chalcone followed by another proton transfer to regenerate the Et‐BAC along with enolic form of the product. Enolic form ultimately transforms into the desired keto form, 1‐(4‐methoxyphenyl)‐2, 4‐diphenylbutane‐1, 4‐dione via protonated and free DBU aided proton shift mechanism. DFT‐derived reactivity parameters along with frontier molecular orbital (FMO) analysis have been successfully utilised to reveal the umpolung efficacy of Et‐BAC. This DFT exploration is in good accordance with experimental findings and also offers a deeper insight into the Et‐BAC catalysed organic transformations. Abstract : A plausible mechanism for the bis(diethylamino)cyclopropenylidene (Et‐BAC) catalyzed synthesis of 1, 4‐diketones has been developed using the density functional theory (DFT) method. The proposed catalytic cycle proceeds through the umpolung strategy, and the in situ generated Breslow intermediate serves the origin of umpolung activity. DFT‐derived reactivity descriptors along with frontier molecular orbital (FMO) analyses have been successfully utilized to unravel the umpolung efficacy of Et‐BAC. This investigation offers deeper insights into the Et‐BAC catalysed organic transformations.