60674-49-9Relevant academic research and scientific papers
Insertion reactions of allenes with palladium aryl complexes [PdI(Ph)(PPh3)]2 and PdI(Ph)(dppe)
Bai, Tao,Xue, Liqin,Xue, Peng,Zhu, Jun,Sung, Herman Ho-Yung,Ma, Shengming,Wiliams, Ian Duncan,Lin, Zhenyang,Jia, Guochen
, p. 2614 - 2626 (2008)
Treatment of [PdI(Ph)(PPh3)]2 with allenes CH 2=C=CHR (R = CMe3, CO2Et, P(O)(OEt) 2, and SO2Ph) in dichloromethane at room temperature produces a mixture of cis and trans isomers of the π-allyl palladium complexes PdI(η3-CH2C(Ph)CHR)(PPh3) in which the R group is anti to the Ph group. The disubstituted alienes MeCH=C=CHR (R = P(O)(OEt)2 and SO2Ph) similarly react with [PdI(Ph)(PPh3)]2 to give the π-allyl palladium complexes PdI(η3-MeCHC(Ph)CHR)(PPh3) in which the R group is anti and the Me group is syn to the Ph group. PdI(Ph)(dppe) alone was found to be unreactive toward allenes such as CH2=C=CHSO 2Ph and MeCH=C=CHSO2Ph at room temperature. In contrast, in the presence of TIPF6, PdI(Ph)(dppe) readily reacts with allenes CH2=C=CHR (R = CMe3, CO2Et, COPh, and SO 2Ph) and MeCH=C=CHSO2Ph to give the π-allyl palladium complexes [Pd(η3-CH2C(Ph)CHR)(dppe)]PF6 and [Pd(η3-MeCHC(Ph)CHR)(dppe)]PF6, respectively. Although mechanistically possible, vinyl complexes were not observed as the insertion products in all cases. The substituents of allenes appear to have no effect on the reaction pathways, at least for the allenes used in this study. The insertion reactions involving PdI(Ph)(PR3)(allene) have been studied by computational chemistry using the model complex PdI(Ph)(MeCH=C= CHSO2H)(PH3).
Achieving vinylic selectivity in Mizoroki-heck reaction of cyclic olefins
Wu, Xiaojin,Lu, Yunpeng,Hirao, Hajime,Zhou, Jianrong
supporting information, p. 6014 - 6020 (2013/06/26)
In Heck reactions of cyclic olefins, the products usually have aryl groups that end up at the allylic and/or homoallylic position. We herein report new selectivity that adds aryl groups to the vinylic position. Cyclic olefins of various ring size worked well. The desired isomers were produced by palladium-hydride-catalyzed isomerization of the initial products. Thus, a specific catalyst must be used so that it can perform two jobs under one set of reaction conditions. Copyright
Unexpected H2O-induced Ar-X activation with trifluoromethylpalladium(II) aryls
Grushin, Vladimir V.,Marshall, William J.
, p. 4632 - 4641 (2007/10/03)
A series of new complexes [(L-L)Pd(Ar)(CF3)] (L-L = dppe, dppp, tmeda; Ar = Ph, p-Tol, C6D5) have been synthesized and fully characterized in solution and in the solid state. Remarkable Ph-X activation (X = I, Cl) by [(dppe)Pd(Ph)(CF3)] (1) has been found to come about to cleanly produce biphenyl and [(dppe)Pd(Ph)(X)]. This reaction does not take place under rigorously anhydrous conditions but in the presence of traces of water it readily occurs, exhibiting an induction period and being zero order in PhI. As shown by mechanistic studies, the role of water is to promote reduction of small quantities of the Pd(II) complex to Pd(0) which activates the Ph-X bond. Subsequent transmetalation to give diphenyl Pd complexes, followed by Ph-Ph reductive elimination give rise to the observed products. The water-induced reduction to catalytically active Pd(0) has been demonstrated to proceed via both the Pd(II)/P(III) to Pd(0)/P(V) redox mechanism and α-F transfer, followed by facile hydrolysis of the difluorocarbene to carbonyl, migratory insertion, and reductive elimination of PhC(X)O (X = F, OH, or OOCPh). In the absence of H2O and ArX, the diphosphine-stabilized trifluoromethyl Pd phenyl complexes undergo slow Ph-CF3 reductive elimination under reinforcing conditions (xylenes, 145 °C).
Studies on the reactivity of isocyanates and isothiocyanates with palladium-imidoyl complexes
Owen, Gareth R.,Vilar, Ramon,White, Andrew J.P.,Williams, David J.
, p. 4511 - 4521 (2008/10/08)
The reactions of palladium-iminoacyl complexes with isocyanates (RNCO) and isothiocyanates (RNCS) have been investigated. The reaction of Pd{C(Me)=NXy}(Cl)(P-P) (P-P = dppe, 1; dppp, 2) with RNCE (E = O, S) in the presence of AgBF4 yields the novel compounds {Pd{C(=CH2)N(Xy)C(=E)NHR}(dppe)][BF4] (E = O and R = Et, 3; Ph; 4; E = S and R = Me, 5; Ph, 6); the formation of these complexes results from an addition reaction followed by the migration of a proton from the methyl group in the imidoyl fragment to the nitrogen in the RNCE moiety. In contrast, the reaction between Pd{C(Ph)=NXy}(I)(dppe) and RNCO in the presence of AgBF4 yields the addition product [Pd{C(Ph)=N(Xy)C(=O)(= NPh)}(dppe)]-[BF4] (10). Protonation of the imidoyl group in Pd{C(Me)=NXy}(Cl)(dppe) suppresses the addition reaction when the protonated complex is reacted with RNCS; the products obtained in this case are [Pd{C(Me)=NHXy}(dppe)(S=C=NR)][BF4]2 (R = Me, 15; Ph, 16).
An exploratory study of regiocontrol iii the heck type reaction. Influence of solvent polarity and bisphosphine ligands
Ludwig, Maik
, p. 970 - 975 (2008/10/08)
The regiochemistry of the addition of arylpalladium species to styrene and propene has been studied. It was found that for the reaction of P2Pd(Ph)X the counterion X, the polarity of the solvent, and the structure of the bisphosphine ligand ?2 all have an influence. Using bis(diphenylphosphino)ethane as ligand, triflate as counterion, and a moderately polar solvent mixture, 98% selectivity for addition of the phenyl group to the /?-carbon of styrene could be obtained. Finally, using low-temperature NMR, some of the palladium intermediates in the addition could be observed, specifically those where the palladium species is stabilized by ?/3-allylic interaction with a phenyl group.
Carbon-sulfur bond-forming reductive elimination involving sp-, sp2-, and sp3-hybridized carbon. Mechanism, steric effects, and electronic effects on sulfide formation
Mann, Grace,Baranano, David,Hartwig, John F.,Rheingold, Arnold L.,Guzei, Ilia A.
, p. 9205 - 9219 (2007/10/03)
Palladium thiolato complexes [(L)Pd(R)(SR')], within which L is a chelating ligand such as DPPE, DPPP, DPPBz, DPPF, or TRANSPHOS, R is a methyl, alkenyl, aryl, or alkynyl ligand, and R' is an aryl or alkyl group, were synthesized by substitution or proton-transfer reactions. All of these thiolato complexes were found to undergo carbon-sulfur bond-forming inductive elimination in high yields to form dialkyl sulfides, diaryl sulfides, alkyl aryl sulfides, alkyl alkenyl sulfides, and alkyl alkynyl sulfides. Reductive eliminations forming alkenyl alkyl sulfides and aryl alkyl sulfides were the fastest. Eliminations of alkynyl alkyl sulfides were slower, and elimination of dialkyl sulfide was the slowest. Thus the relative rates for sulfide elimination as a function of the hybridization of the palladium-bound carbon follow the trend sp2 > sp >> sp3. Rates of reductive elimination were faster for cis-chelating phosphine ligands with larger bite angles. Kinetic studies, along with results from radical trapping reactions, analysis of solvent effects; and analysis of complexes with chelating phosphines of varying rigidity, were conducted with [Pd(L)(S-tert-butyl)(Ar)] and [Pd(L)(S- tert-butyl)(Me)]. Carbon-sulfur bond-forming reductive eliminations involving both saturated and unsaturated hydrocarbyl groups proceed by an intramolecular, concerted mechanism. Systematic changes in the electronic properties of the thiolate and aryl groups showed that reductive elimination is the fastest for electron deficient aryl groups and electron rich arenethiolates, suggesting that the reaction follows a mechanism in which the thiolate acts as a nucleophile and the aryl group an electrophile. Studies with thiolate ligands and hydrocarbyl ligands of varying steric demands favor a migration mechanism involving coordination of the hydrocarbyl ligand in the transition state.
