50996-97-9Relevant academic research and scientific papers
Acylation of dimethyl maleate photocatalyzed by decatungstate anion: insights into the hydrogen atom transfer reaction mechanism
Martínez, Juan Pablo,Rivera-Avalos, Ernesto,Vega-Rodríguez, Sarai,de Loera, Denisse
, p. 2061 - 2073 (2018)
Polyoxometalates arise as significant catalysts in the field of organic chemistry due to their diverse properties and functions. Recent progress based on experimental evidence and density functional theory (DFT) calculations provides valuable information to demystify the chemistry of decatungstate anion, W10O32 4?. Particularly, functionalization of aldehydes by homolytic C–H bond cleavage can be efficiently achieved when it is catalyzed by this polyoxometalate. Two reaction mechanisms have been formulated to account for the role of W10O32 4? in organic chemical reactions: the single electron transfer and the hydrogen atom transfer (HAT) mechanisms. In this contribution, the HAT pathway for the acylation of dimethyl maleate is experimentally and quantum-chemically explored in detail. Results based on DFT calculations under the unrestricted formalism suggest that the acylation occurs in a barrierless process upon the formation of the lowest-in-energy triplet excited state of W10O32 4?. These outcomes agree well with the experimental evidence since the acylated adduct was produced at a 90% yield; in this regard, side reactions like radical couplings and decarbonylation resulted in less competitiveness. The current work may therefore help in the comprehension of the mechanistic details leading to the synthesis of organic compounds photocatalyzed by polyoxometalates, even under solar radiation.
Photochimie en solution. XXIV. Mecanisme de l'addition des aldehydes aux double liaisons ethyleniques activees par des groupements attracteurs d'electrons
Kawenoki, Isabelle,Maurel, Daniele,Kossanyi, Jean
, p. 385 - 390 (2007/10/02)
The mechanism of the photochemical addition of aliphatic aldehydes to electron-deficient olefins has been rationalized.No addition to α,β-unsaturated ketones was observed when the latter were excited.The reaction can be explained by a first self-quenching step of the aliphatic aldehyde involving its lowest triplet state, which is reached with a moderate quantum yield (0.5).The radical R-C.=O produced in the self quenching process adds to the olefin at the more positively-charged carbon atom.The reaction ends by a hydrogen atom exchange between the radical produced by this addition and the radical R-C.HOH.The quantum yield of the product formation is much higher with benzaldehyde owing to the almost unity value of the intersystem crossing, but it competes with the formation of benzile.
