Palladium triflate catalyst

The palladium-catalyzed cross-coupling reaction featured in this procedure occurs under neutral conditions in the presence of many synthetically useful functional groups (e.g. alcohol, ester, nitro, acetal, ketone, and aldehyde). The reaction works best in N,N-dimethylformamide with bis(triphenylphosphine)palladium(ll) chloride, PdCI2(PPh3)2, as the catalyst. Lithium chloride is added to prevent decomposition of the catalyst.143 13 It is presumed that conversion of the intermediate aryl palladium triflate to an aryl palladium chloride is required for the transmetallation step to proceed.9... 

Tributylstannyl)-3-cyclobutene-1,2-diones and 4-methyl-3-(tributylstan-nyl)-3-cyclobutene-l,2-dione 2-ethylene acetals undergo the palladium/copper-catalyzed cross coupling with acyl halides, and palladium-catalyzed carbon-ylative cross coupling with aryl/heteroaryl iodides [45]. The coupling reaction of alkenyl (phenyl )iodonium triflates is also performed by a palladium/copper catalyst [46],... 

Palladium-catalyzed bis-silylation of benzynes has been achieved. Reaction of 2-trimethylsilylaryl triflates with cyclic disilanes in the presence of KF/18-crown-6 affords cyclic bis-silylation products in good yields (Equation (29)). It is crucially important to use the palladium-isocyanide catalyst.99 100... 

The rhodium(II) catalysts and the chelated copper catalysts are considered to coordinate only to the carbenoid, while copper triflate and tetrafluoioborate coordinate to both the carbenoid and alkene and thus enhance cyclopropanation reactions through a template effect.14 Palladium-based catalysts, such as palladium(II) acetate and bis(benzonitrile)palladium(II) chloride,l6e are also believed to be able to coordinate with the alkene. Some chiral complexes based on cobalt have also been developed,21 but these have not been extensively used. 

The mechanism involves oxidative addition of the halide or triflate to the initial palladiumfO phosphine complex to form a palladium(II) species. The key slow step is a transmetallation, so calk because the nucleophile (R1) is transferred from the metal in the organometallic reagent to the palla dium and the counterion (X = halide or triflate) moves in the opposite direction. The new palladi um(II) complex with two organic ligands undergoes reductive elimination to give the couple product and the palladium(O) catalyst ready for another cycle. 

In the 1980s Drent and colleagues at Shell found a remarkable change in catalytic behaviour when monodentate phosphines were replaced with certain bidentate diphosphines. Cationic palladium(II) catalysts generated in methanol from Pd(OAc)2, PPhs and the acid of a weakly coordinating anion (e.g. tosylate, triflate) catalyzed the methoxycarbonylation of ethylene to... 

A fourth type of product, a carbamate RNHCOOR , can be obtained from primary or secondary amines, if these are treated with CO, O2, and an alcohol R OH in the presence of a catalyst. " Primary amines react with dimethyl carbonate in supercritical CO2 (see p. 414) to give a carbamate. " Carbamates can also be obtained from nitroso compounds, by treatment with CO, R OH, Pd(OAc)2, and Cu(OAc)2, " and from nitro compounds. " When allylic amines (R2C=CHRCHRNR 2) are treated with CO and a palladium-phosphine catalyst, the CO inserts to produce the p,y-unsa-turated amides (R2C=CHRCHRCONR 2) in good yields. " Ring-expanded lactams are obtained from cyclic amines via a similar reaction (see also, 16-22). Silyloxy carbamates (RNHC02SiR 3) can be prepared by the reaction of a primary amine with carbon dioxide and triethylamine, followed by reaction with triisopropylsilyl triflate and tetrabutylammonium fluoride. ... 

The basic mechanism of the Heck reaction (as shown below) of aryl or alkenyl halides or triflates involves initial oxidative addition of a pal-ladium(O) species to afford a a-arylpalladium(II) complex III. The order of reactivity for the oxidative addition step is I > OTf > Br > Cl. Coordination of an alkene IV and subsequent carbon-carbon bond formation by syn addition provide a a-alkylpalladium(II) intermediate VI, which readily undergoes 3-hydride elimination to release the product VIII. A base is required for conversion of the hydridopalla-dium(II) complex IX to the active palladium(O) catalyst I to complete the catalytic cycle. 

A-Glycosylimidazoles (related to nucleosides) are of interest in the preparation of novel chemotherapeutic agents, hence selective A -glycosylation techniques are of interest. The palladium-catalyzed addition of vinyl epoxides and allyl acetates to imidazoles provides one such route to imidazole nucleoside analogues <91JCS(Pi)2603, 9UOC4990>. The silyl-Hilbert-Johnson method is another in which the imidazole is silylated, then treated with a suitable peracetylated carbohydrate derivative in the presence of trimethylsilyl triflate catalyst. With 4-carbamoylimidazolium-5-olate, for example, the major product is the l-glycosyl-5-carbamoyl isomer with only low yields of the... 

The vinyl triflate 109 is prepared in high yield by the reaction of the TBS ether 110 with A/-phenyltrifluoromethanesulphonimide (Tf2NPh) in the presence of LDA. A coupling reaction of the triflate 109 with methyl acrylate, in the presence of a palladium-(ll)-catalyst. 

In a one-pot procedure, the reaction of o-iodoanilines 219 with silylaryl triflates 220 in the presence of cesium fluoride affords via an aryne intermediate the o-iododiar-ylamines 221 which are subsequently cyclized to carbazoles 32 by an in situ generated palladium(O) catalyst (Scheme 52) [211, 212]. 

This palladluin-catalysed addition of aryl, vinyl, or substituted vinyl groups to organic halides or triflates is one of the most synthetically useful palladium-catalysed reactions. The methcxl is very efficient, and carries out a transformation that is drffitailt by more traditional techniques. The medianism involves the oxidative addition of the halide, Insertion of the olefin, and elimination of the product by a P-hydride elimination process. A base then regenerates the palladium(0) catalyst. The whole process is a catalytic cycle. 

The mechanism involves the oxidative addition of the vinyl or aromatic triflate or halide to give an organopalladium intermediate. TransmetaUation with the organostannane forms another organopalladium intermediate with two Pd—C a bonds. A reductive elimination step releases the product and thereby regenerates the palladium(0) catalyst. Vinyl triflates can be made from enolizable aldehydes or ketones and aryl triflates from phenols, but the reaction also works with vinyl and aryl halides. 

Complexes containing P(t-Bu)3 as ligand will also catalyze the reaction of unactivated aryl chlorides with diarylamines. Thus far, the reaction of aryl triflates with diarylamines has only been reported with catalysts bearing chelating phosphines. A few representative examples of the reactions of diarylamines with aryl triflates do occur in nearly quantitative yield when using DPPF-ligated palladium as catalyst. Reactions of diarylamines with aryl nonaflates as part of the synthesis of discrete oligomeric triarylamines has also been reported. ... 

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