Reversible Formation of a Cationic Palladium(II) Hydride [HPd(PPh3)2]+ in the Oxidative Addition of Acetic or Formic Acid to Palladium(0) in DMF

Palladium0-catalyzed isomerization of (Z)-1-functionalized-4-acetoxy-2-butenes: Solvent and substituent effects

“…This is highlighted from 1 Sp and 1 Sm , and could be due to the coordinating properties of DMF towards the transition metals [4,5,8,9]. It is known that DMF can substitute coordinated PPh 3 [10], and that the equilibria attained from the Pd 0 -catalyzed 1,3-transposition of allylic acetates is ligand dependent [11]. Thus, coordination of DMF to the palladium intermediates depicted in Scheme 3 can have an effect on equilibria and reaction rates.…”

Cationic Palladium Complex-Catalyzed Cyclization-Hydrosilylation of 1,6-Heptadiyne and its Homologs

“…Cycloisomerization of linear enynes using Pd(0) and an acid, [cationic palladium hydride], 13 to give cyclic dienes has been extensively exploited most notably by Trost. 14 Similar to a possible catalytic cycle for this transformation, 15 the cyclization-hydrosilylation of a,w-diynes would proceed as follows (Scheme 5): Following (i) complexation, (ii) hydropalladation, and (iii) intramolecular carbopalladation, the cyclized (Z)-alkenylpalladium intermediate is formed and finally undergoes (iv) a possible s-metathesis with a hydrosilane 16 to give the silylated product, regenerating the cationic catalyst.…”

“…(8) Spectral data for 2b: 1 H NMR (270 MHz, CDCl 3 ): d (ppm) = 1.21 (t, J = 6.9 Hz, 1 H), 3.08 (br t, J = 2.2 Hz, 2 H), 3.13 (br d, J = 1.7 Hz, 2 H), 3.72 (s, 6 H), 3.80 (q, J = 6.9 Hz, 6 H), 5.17 (br t, J = 2.2 Hz, 1 H), 5.32 (br t, J = 2.0 Hz, 1 H), 5.95 (t, J = 2.3 Hz, 1 H). 13 C NMR (67.8 MHz): d (ppm) = 18.1 (× 3), 42. 1, 45.1, 52.8, 56.9, 58.4 (× 3), 112.0, 112.5, 143.7, 158.3, 171.6.…”

Electrosynthesis of heteroaromatic aldehydes by palladium-catalyzed carbonylation of heteroaromatic iodides in the presence of formic acid

“…As a matter of fact, the synthesis of aryl aldehydes from aryl halides, CO and formic acid is formally an hydride transfer from HCOO À . Formate ions cannot be supplied directly from formic acid; in fact, the dissociation constant of formic acid in DMF is too low to allow it to be the direct source of formate ions [8]. Moreover, formic acid cannot be the direct source of formate ions by electrochemical reduction of its protons.…”

“…(1) is continuously displaced to its right-hand side, generating a small but constant flux of formate ions. The result is that formate ions are generated at an adequate rate via a combination of chemical and electrochemical steps, at a potential where the direct reduction of formic acid to formate and H 2 cannot occur [8]. When the electrochemical reduction of aryl halides was carried out under 1 atm of CO, in the presence of catalytic amount of PdCl 2 (PPh 3 ) 2 and formic acid, aromatic aldehydes were isolated in high yields [9].…”