Cross-coupling tetrakis palladium

The synthesis of the second Stille coupling partner 34 was efficiently achieved in three steps. First, 2-bromojuglone (36) [28] was protected as its methoxymethyl ether (46, Scheme 3.7). The quinone was reduced using sodium thiosulfate, and the resulting hydroquinone was protected with methoxymethyl chloride to afford the arene 47. Finally, stannylation using tetrakis-(triphenylphosphine)palladium and hexabutylditin [29] afforded the cross-coupling partner 34 in high yield. 

Trialkylstannyl groups can also be replaced by reactive electrophiles in certain cases, but most commonly stannylated azaheterocycles are employed in palladium catalyzed cross-coupling reactions [85PAC1771 86AG(E)508 92S413]. For example, trimethylstannylpyridines can be reacted with bromopyridines in the presence of catalytic amounts of tetrakis-(triphenylphosphine)palladium to give a variety of different bipyridines (Scheme 158)(86S564). 

Polymers were prepared using Suzuki cross coupling with tetrakis triphenylphosphine palladium (0). 

Cross-coupling of two vinyl groups Dichlorobis(triphenylphosphine)pal-ladium(II), 103 Palladium(II) acetate, 232 Tetrakis(triphenylphosphine)palla-dium(0), 289... 

Thus, for our present purposes a similar approach was followed using Suzuki cross-coupling reactions as the key steps in the synthesis of our target compounds. Symmetrically substituted compounds were synthesized in a twofold Suzuki crosscoupling reaction from commercially available p-substituted phenylboronic acids or esters and 4,4 -dibromobiphenyl or 4,4 -biphenyl-bis-boronic acid ester and a p-substituted arylhalide, respectively, using tetrakis (triphenylphosphino) palladium as catalyst together with cesium fluoride as base in dry tetrahydrofurane as shown in Scheme 8.1. The desired products were obtained in respectable yields after heating at reflux for 50 h. 

A similar Suzuki cross-coupling reaction has also been employed by Gill and Lubell in a synthesis of an unsaturated kainoid analogue.50 Vinyl triflates 97 and 98 were cross-coupled with phenylboronic acid using tetrakis(triphenylphosphine)palladium(0) to give the corresponding coupled products 99 and 100 with high efficiencies (Scheme 42). 

Enynes can also be synthesized in excellent yields with high regio- and stereoselectivity by transition metal catalyzed cross-coupling reaction. Thus, ( >l-alkenyl-disiamylboranes react with 1-halo-1-alkynes in the presence of catalytic amount of tetrakis(tripheny]phosphine)palladium to afford conjugated trans enynes (Eq. 100)145). 

Tetraki s(tri phenyl phosphine) palladium was prepared by treating palladium chloride, available from Matthey Bishop, Inc., with hydrazine hydrate 1n the presence of triphenyl phosphine according to an Inorganic Syntheses procedure. The submitters used a freshly prepared, shiny yellow, crystalline sample of the palladium complex. On standing for an extended period of time (> a few weeks), its color gradually darkens. Even such samples are effective in many palladium-catalyzed cross-coupling reactions, but have not been tested in this reaction. Tetraki s( tri phenyl phosphine) palladium is also available from Aldrich Chemical Company. 

Vinylic ethers (44) can be synthesized in high yields by the cross-coupling of aryl or benzyl halides with tris(2-ethoxyvinyl)borane (4S) in the presence of 1 molej% of a palladium compound such as tetrakis(triphenylphosphine)palladium and a base (Eq. 108) Since vinylic ethers (44) thus obtained can readily be hydrolyzed to aldehydes, this reaction provides a convenient procedure for converting aryl or benzylic halides into the corresponding aldehydes with two more carbon atoms. 

Reaction of 6-iodo-9-(2,3,5-tri-0-acetyl-/3-D-ribofurano.syl)purine with tetramethyltin in the presence of tetrakis(triphenylphosphane)palladium(0) gives, after deprolection, 6-methyl-9-(/(-D-ribofurano.syl)purine 22 (Stille cross coupling). This is the most straightforward synthesis for this type of compound described in the literature. 

Fig. 3 Common reactions and cross-couplings in oligofluorene synthesis shown for example structures, where PdCl2(dppf) is [l,l -bis(diphenylphospino)ferrocene] dichloropaUadium(II), Pd(PPh3)4 is tetrakis(triphenylphosphino)palladium(0), and Ni(COD) is bis(l,5-cyclooctadiene)nickel(0)... 

To the vinyl iodide (1.442 g, 4.938 mmol) in benzene (100 mL) was added vinyl magnesium bromide (1.0 M in THF, 19.75 mL, 19.75 mmol) and tetrakis(triphenylphosphine) palladium (286 mg, 0.247 mmol). Note degassing of the solvent is usually recommended for palladium cross-coupling reactions. This reaction mixture was heated to 60-70 °C for 30 min, diluted with hexanes, and filtered through a pad of silica. After evaporation of the solvents, bulb to bulb Kugelrohr distillation provided 834 mg (88%) of the triene as a colorless oil. 

The 2-bromododeca-l,ll-dien-6-yne derivative 461 undergoes a triple cyclization, followed by rearrangement, under the influence of a palladium catalyst to yield 462. Cross-coupling of the iodo compound 463 with ( )-l-hexen-l-ylzinc chloride in the presence of tetrakis(triphenylphosphine)palladium yields 68% of the indane 464 and 19% of the uncyclized product 465 ". ... 

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