134391-08-5Relevant academic research and scientific papers
Chemodivergent Photocatalytic Synthesis of Dihydrofurans and β,γ-Unsaturated Ketones
Quintavalla, Arianna,Veronesi, Ruben,Carboni, Davide,Martinelli, Ada,Zaccheroni, Nelsi,Mummolo, Liviana,Lombardo, Marco
, p. 3267 - 3282 (2021)
A synthetic procedure, catalysed by Ir(ppy)3 under visible-light irradiation, for the chemodivergent synthesis of 2,3-dihydrofurans (3) or β,γ-unsaturated ketones (7) starting from α-halo ketones (1) and alkenes (2) has been developed. The mild reaction conditions and the redox-neutral nature of the process make it particularly sustainable avoiding the use of both sacrificial reactants and stoichiometric strong oxidants. Careful experimental investigations, supported by DFT calculations, allowed to disclose in details a possible mechanistic pathway and to direct the synthesis chemodivergently either toward 3 or 7, depending not only on the nature of the substrates, but also on the choice of the experimental conditions. (Figure presented.).
Electronic and Steric Effects in the Addition of Electrophilic 1,3-Dicarbonylalkyl Radicals to Styrenes
Baciocchi, Enrico,Ruzziconi, Renzo
, p. 4772 - 4778 (2007/10/02)
The addition reactions of 1,3-dicarbonylalkyl radicals to ring-substituted styrenes have been kinetically investigated in MeOH and/or MeCN.It has been observed that the rate effect of ring substituents is nearly identical in the reactions of MeCOCHCOMe (1), MeOCOCHCOMe (2) and MeOCOCHCOOMe (4), the ρ value, in MeOH being -0.96, -1.01 and -1.06, respectively.Since the three radicals are relatively strong oxidants and have similar reduction potentials, an important contribution of the transfer structure RCOCHCOR(1-)*CH2CHAr(1+) to the addition transition state is suggested.It has also be found that in the reactions of 1 and 4 with α-alkyl-substituted styrenes the rate of additions is strongly influenced by the nature of the alkyl group, decreasing in the order: Me > Et > i-Pr > t-Bu.The observed effects are much larger than those reported for the corresponding reactions of the nucleophilic cyclohexyl radical.It is suggested that the α-alkyl substituents exert an effect of steric inhibition of resonance thereby ring delocalization of the charge and/or unpaired electron in the transition state is significantly reduced.Delocalization may be more important in the reactions of 1 and 4 than in those of the cyclohexyl radical since it is possible that the former utilizes a transition state occurring later along the reaction coordinate and/or characterized by a larger extent of charge transfer.
