New synthetic applications of water-soluble acetate Pd/TPPTS catalyst generated in Situ. evidence for a true Pd(0) species intermediate

Abstract

Studies on the sp-sp intermolecular coupling reactions with the palladium water-soluble catalyst prepared in situ from palladium(I1) acetate and sulfonated triphenylphosphine P(C&bz-S03Na)3 (TPPTS) in a homogeneous acetonitrile-water system, without Cu(1) promotor, afford diynes with moderate yields (45-65%). Under the same conditions, the sp2-sp coupling of 2-iodophenols or 2-iodoanilines and terminal alkynes followed by intramolecular cyclization gives indolic and furanic products in good yields (60-99%). Under these aqueous conditions, an efficient and short synthesis of eutypine illustrated the synthetic potentiality of the coupling. Furthermore, through a series of kinetic and 31P NMR experiments, we have demonstrated that a mixture of Pd(0Ac)z and TPPTS affords spontaneously a palladium(0) complex, through formation of bivalent complex Pd(0Ac)z-(TPPTS)2. A detailed mechanism of the reaction has been investigated thoroughly and the pertinent rate constants measured. The resulting palladium(0) complex reacts with phenyl iodide via an oxidative addition. This complex is considerably less reactive than the corresponding complex generated from PPh3, probably due to steric effects.

Mechanisms of the Mizoroki–Heck Reaction

“…The formation of the Pd(0) complex follows a Hammett correlation with a positive slope [20]. The more electron-deficient the phosphine, the faster the reduction process; this is in agreement with the intramolecular nucleophilic attack of the acetate onto the ligated phosphine as proposed in Scheme 1.13; (ii) aliphatic phosphines [20]; (iii) water-soluble phosphines, triphenylphosphine trisulfonate (trisodium salt) [25] and triphenylphosphinetricarboxylate (trilithium salt) [26]. One major exception is the tri-o-tolylphosphine P(o-Tol) 3 , which cannot reduce Pd(OAc) 2 to a Pd(0) complex in DMF or THF.…”

Biphasic Catalyzed Telomerization of Butadiene and Ammonia: Kinetics and New Ligands for Regioselective Reactions

“…Studies of the analogous reaction with palladium acetate and triphenylphosphane by Amatore et al [5] show that the half-time for catalyst formation is 106 seconds at 60 8C. Therefore, all reactants except ammonia were placed in the reactor, which was then heated to reaction temperature (80 8C).…”

“…The phases were separated, and the organic phase was dried over a 4 molecular sieve and analyzed by GC. Further samples were taken after 5,10,15,20,25,30 and 40 min reaction time. Once the reaction was finished, the unreacted butadiene was burned with a bunsen burner.…”

Stereoselective Synthesis of (E)- and (Z)-Acetals of Pent-2-en-4-yn-1-al and Related Dienynes and Dienediynes

“…While the desired product 4a-E was often obtained as the major compound (Scheme 2), considerable E and 6 were obtained by an anti-retrohydropalladation. [22] Obviously, obtaining 4a-E according to Scheme 3 is one amounts of side products were also observed when the reaction was performed at room temperature. Using triethyl-possibility among more conventional ones.…”