Vinylic, allylic and homoallylic oxidations of alkenes via π- and σ-organopalladium complexes

Correlation of Relative Rates of PdCl2 Oxidation of Functionalized Acyclic Alkenes versus Alkene Ionization Potentials, HOMOs, and LUMOs

“…The next step (eq 3) in the reaction sequence is generally accepted to be the nucleophilic replacement of a second chloride by water to give intermediate 3 . There seems to be agreement that the previous equilibrium steps (eqs 2 and 3) in the reaction sequence are fast relative to the rates of the subsequent steps. − However, two different pathways have been suggested for the following step ( 3 → 5 ) (eqs 4 and 4‘). In the first pathway, the alkene complex 3 deprotonates first to a negative hydroxymetal complex ion 4 (eq 4), followed by rate-determining conversion of the palladium(II) alkene π-complex into a palladium(II) β-hydroxyalkyl species 5 , a process called hydroxypalladation (eq 4) .…”

“…There has been much interest − in the mechanism of palladium chloride (PdCl 2 ) oxidation (eq 1) of acyclic alkenes. This is in part due to the industrial importance 3,4 of the reaction in the synthesis of carbonyl compounds from corresponding alkenes (the Wacker oxidation 3a,b ) and in part due to the interest in its mechanistic pathway. − The steps of the reaction are now generally considered to be those shown below (eqs 2−7), although there has been disagreement over some mechanistic details and over the identity of the rate-determining step. − The first step (eq 2) of the reaction is alkene coordination to give a palladium(II) complex 2 . The next step (eq 3) in the reaction sequence is generally accepted to be the nucleophilic replacement of a second chloride by water to give intermediate 3 .…”

Use of CuO encapsulated in mesoporous silica SBA-15 as a recycled catalyst for allylic C–H bond oxidation of cyclic olefins at room temperature

“…8 The nature of the metal salt, perester oxidant, and reaction conditions including solvent and temperature are affected this reaction remarkably. [9][10][11][12][13][14][15][16][17] Allylic C-H bond oxidation have been studied by homogeneous catalysts such as selenium, [18][19][20][21][22][23][24] selenium dioxide, [18][19][20][21]23 diselenides 24 and pentauorobenzeneselenic acid [18][19][20][21][22][23][24] with different metals such as Hg(II), [25][26][27][28][29][30] Pd(II), [31][32][33][34][35][36][37] Pb(IV), 25 Cr(VI), 25,38,39 Co(III), 40,41 Co(II),…”

Palladium-Catalysed Oxidation of Bicycle Monoterpenes by Hydrogen Peroxide in Acetonitrile Solutions: A Metal Reoxidant-Free and Environmentally Benign Oxidative Process

“…Thus, based on work of Gusevskaya and co-workers [24], who proposed interesting routes for the formation of both epoxy-camphene (1a) and glycol camphene (1b), we suggested a similar pathway for the PdCl 2 -catalysed camphene oxidation by peroxide hydrogen (see Scheme 1). Probably, palladium hydroperoxidic species (ClPdOOH and/or HOPdOOH) obtained by the addition of hydrogen peroxide to palladium chloride seems to be the most likely active intermediate in this system [29]. Thus, after peroxypalladation of the camphene double bond, which results in a p-camphene-palladium complex, a further step of reductive elimination of HPdOOH species generates finally the epoxi-camphene (1a) (Scheme 1).…”

“…i.e., H 2 O 2 and/or H 2 O on the substrate coordinated to palladium in a p-allylic fashion (see Scheme 5) [29,33]. Even though the weakness of both nucleophiles; however, a comparison in terms of reactivity is difficult, because they are present in the solution in different amounts, and both could be involved in the oxidation of (2).…”