147159-76-0Relevant academic research and scientific papers
Tandem Acid/Pd-Catalyzed Reductive Rearrangement of Glycol Derivatives
Ciszek, Benjamin,Fleischer, Ivana,Kathe, Prasad,Schmidt, Tanno A.
, p. 3641 - 3646 (2020/03/25)
Herein, we describe the acid/Pd-tandem-catalyzed transformation of glycol derivatives into terminal formic esters. Mechanistic investigations show that the substrate undergoes rearrangement to an aldehyde under [1,2] hydrogen migration and cleavage of an oxygen-based leaving group. The leaving group is trapped as its formic ester, and the aldehyde is reduced and subsequently esterified to a formate. Whereas the rearrangement to the aldehyde is catalyzed by sulfonic acids, the reduction step requires a unique catalyst system comprising a PdII or Pd0 precursor in loadings as low as 0.75 mol % and α,α′-bis(di-tert-butylphosphino)-o-xylene as ligand. The reduction step makes use of formic acid as an easy-to-handle transfer reductant. The substrate scope of the transformation encompasses both aromatic and aliphatic substrates and a variety of leaving groups.
Alkoxyl Radicals Generated under Photoredox Catalysis: A Strategy for anti-Markovnikov Alkoxylation Reactions
Barthelemy, Anne-Laure,Tuccio, Béatrice,Magnier, Emmanuel,Dagousset, Guillaume
supporting information, p. 13790 - 13794 (2018/09/10)
Reported herein is a novel photoredox-catalyzed approach for ether synthesis and it involves alkoxyl radicals generated from N-alkoxypyridinium salts. A wide range of alkenes are smoothly difunctionalized in an anti-Markovnikov fashion, affording various functionalized alkyl alkyl ethers. Notably, this mild process tolerates a number of functional groups and is efficiently carried out under both batch and flow conditions. Importantly, electron paramagnetic resonance (EPR) experiments by spin trapping were carried out to characterize the radical intermediates involved in this radical/cationic process.
A kinetic evaluation of carbon-hydrogen, carbon-carbon, and carbon-silicon bond activation in benzylic radical cations
Freccero, Mauro,Pratt, Albert,Albini, Angelo,Long, Conor
, p. 284 - 297 (2007/10/03)
A detailed study of the competition between C-C, C-H, and C-Si bond fragmentation in a series of 4-methoxy-α-substituted toluene radical cations (1.+), involving both product studies and kinetic analysis, is presented. C-C bond fragmentation occurs with several radical cations in acetonitrile. The rate constants for such processes, determined by laser flash photolysis, varied from 2.8 x 104 (1c.+) to 1.53 x 106 (1f.+) s-1. The activation parameters for C-C bond fragmentation are characterized by low activation enthalpies on the order of 30 kJ mol-1 and negative activation entropies in the range -34 to -55 J mol-1 K-1. Deprotonation of the radical cations is always a second-order process induced by nucleophiles [cerium(IV) ammonium nitrate (CAN) or nitrate anion], with second-order rate constants from 7.7 x 107 (1h.+) to 8.8 x 108 (1i.+) M-1 s-1 in neat acetonitrile (CAN assisted) and from 0.4 x 108 (1j.+) to 7.1 x 108 (1i.+) M-1 s-1 in the presence of nitrate anion. The rate constant for nitrate-induced decarboxylation was higher, 13.6 x 108 M-1 s-1 (1d.+). In a few cases C-C (1e.+, 1f.+) and C-Si (1g.+) fragmentations occurred, also as second-order processes induced by nitrate, with rate constants from 4.4 x 108 (1f.+) to 8.2 x 108 (1g.+) M-1 s-1. ΔH and ΔS had opposing influences on C-H and C-C fragmentation, and in the case of 1e.+ a temperature-dependent product distribution was obtained. The activation parameters for the observed C-H, C-C, and C-Si fragmentations have been compared, and suggest a rationale for the mechanisms and selectively of such processes in radical cations.
Effects of Para-Substituents on the Mechanisms of Solvolysis of Styrene Oxides
Blumenstein, Jeffrey J.,Ukachukwu, Victoria C.,Mohan, Ram S.,Whalen, Dale L.
, p. 924 - 932 (2007/10/02)
Rate and product studies of the hydronium ion-catalyzed, hydroxide ion-catalyzed, and spontaneous reactions of styrene oxide and its p-CH3O, p-CH3, p-Cl, and p-O2N-derivatives in water solutions have been carried out.A Hammett correlation of log k for the acid-catalyzed reactions vs ?+ gives a slope ρ+ of -4.2 and only diol products are formed.An intermediate in the hydronium ion-catalyzed hydrolysis of p-methoxystyrene oxide is trapped, subsequent to its rate-limiting formation, by azide ion.The spontaneous reactions of p-methylstyrene oxide and styrene oxide yield only diol products, and their reactions in 18O-water indicate that >/= 98percent and ca. 95percent, respectively, of 18O is incorporated into the benzyl positions.Nucleophilic addition of water to the benzyl carbon of neutral epoxide is proposed as the mechanism of the primary component of the spontaneous reaction for the p-CH3-, p-H- and p-Cl-substrates on the basis of a Hammett ρ of -2.0.The spontaneous rate constant for reaction of p-methoxystyrene oxide is much greater than that expected from a Hammett correlation for the p-CH3, p-H-, and p-Cl-styrene oxides.This increased rate is attributed to the incursion of a reaction that yields mainly (>80percent) p-methoxyphenylacetaldehyde.The regiochemistries of addition of hydroxide ion in 18O-water to p-CH3-, p-H-, and p-Cl-, and p-O2N-substituted styrene oxides were also determined and found to vary as functions of the para substituent.Addition of hydroxide and methoxide ions to the α-carbon is favored by electron-donating groups in the phenyl ring, and addition of these nucleophiles to the β-carbon is favored by electron-withdrawing groups in the phenyl ring.
