Palladium catalysed coupling

Stereo- and regioselective synthesis of trienes and tetraenes has been reported by palladium-catalysed coupling of (E)- or (Z)-l-alkenyl boronates with (E)- or (Z)-2-bromo-1-phenylthio-l-alkenes followed by treatment with a Grignard reagent in the presence of a nickel catalyst (equation 146)259. 

Vinyl ethers stannylated in the a-position undergo palladium-catalysed coupling with aryl hlides, as shown, for example, in reaction 64312 and 65313a. 

The trienedione 7 was prepared using a sequence in which palladium-catalysed couplings were featured, (Scheme 8). In addition, the alkyne moiety of the chloroenyne 8 was partially reduced and the secondary alcohol group oxidised to give the dienone 9. 

The palladium catalysed coupling of trimethylsilylacetylene and the iodopyridone derivative shown in 3.57. led to the formation of the corresponding ethynylpyridine. The absence of the spontaneous ring closure to furo 2,3-/)]pyndinc might be attributed to the preference of the pyridone form over the hydroxypyridine form. Addition of a copper catalyst and base, however, led to the closure of the fiiian ring (3.57.),73 The same approach was utilised in the functionalization of uracil based nucleosides.74... 

Palladium-catalysed coupling also proceeded readily, carbonylative coupling in the presence of alcohols affording some particularly useful C-3 building blocks (Sect. 4.6) (Eq. 71) [224]. A metal-free method for generation of the trifluoroacetimidoyl carbanion has also been reported involving silic-ate formation and trapping [225]. 

Heck-, Suzuki- and Stille-type Couplings - The Heck reaction, palladium-catalysed coupling of aryl or vinyl halides with alkenes or alkynes, is an extremely useful synthetic method. Only recently have Heck reactions been performed in aqueous media, probably due to the perception that water must be carefully... 

Fagnola, M. C. Candiani, I. Visentin, G. Cabri, W. Zarini, F. Mongelli, N. Bedeschi, A. Solid-Phase Synthesis of Indoles Using the Palladium-Catalysed Coupling of Alkynes with Iodoaniline Derivatives, Tetrahedron Lett. 1997, 38, 2307-2310. 

Bromo-3-[2-(t-butoxy carb onylamino)- 2-(ethoxy -carbonyl)ethenyl]-l-(4-methylphenylsulfonyl) B Arvlation by palladium-catalysed coupling 2-Methylbut-3-en-2-ol, Pd(PPh3)2Cl2, Ag2C03, Et3N 83 [3]... 

Palladium-catalysed coupling reactions under carbon monoxide have been extensively used in traditional medicinal chemistry72. Despite this, these crucial transformations have hardly been employed in combinatorial chemistry. These shortcomings have recently been recognised and a series of microwave-heated carbonylative transformations with solid or liquid CO-sources have been reported. 

Larhed, M. and Hallberg, A., Microwave-promoted palladium-catalysed coupling reactions, /. Org. Chem., 1996, 61, 9582-9584. 

Littke, A.F. and Fu, G.C., Palladium-catalysed coupling reactions of aryl chlorides, Angew. Chem., Int. Ed. Engl, 2002,41,4176-4211. 

It has been found that the use, as ligands, of electron-poor phosphines, such as 1,1 -bis(diphenylphosphino)ferrocene, enhances yields ill the palladium-catalysed reaction of aiyl bromides with sodium phenoxides to yield diaryl ethers.87 Palladium-catalysed coupling of ethynylated derivatives of bipyridine or terpyridine with the corresponding bipyridine or terpyridine hahdes or triflates has been used in the synthesis of preorganized polytopic ligands.88... 

Thus the alkyl ester end groups of convergently grown poly(benzyl ether) dendrimers can be subjected to post-synthetic modification by hydrolysis [28], reduction [29], transesterification/amidation [28] in a variety of ways. Subsequent modification of poly(benzyl ether) dendrons bearing p-bromobenzyl end groups by palladium-catalysed coupling reactions permitted preparation of dendrons with phenyl, pyridinyl, or thiophenyl end groups [30]. 

Palladium catalysed coupling reaction of a heteroaromatic zinc compound with a functionalized aryl iodide preparation of N-benzyl-6-(4-ethylcarboxyphenyi)-purine33... 

Using this method, several mesogen diacetylenes were obtained [49]. Palladium-catalysed coupling of an allylic cyclic carbonate with 1-pentynyl phenyliodonium tetrafluoroborate to give an enyne was highly successful [50]. Alkynyl iodonium triflates and lithium salts of diethyl 2-[(diphenylmethylene)amino]malonate were used for the preparation of alkynyl-a-amino acid derivatives, e.g. [51] ... 

Primary phosphines are unpleasant and toxic reagents. They can be prepared from phosphonous halides, RPCI2, using LiAlILt. As is the case for secondary phosphines, easy access to pure phosphonous halides are required to make this route efficient. It has been found that compound 28 can be reduced to primary phosphine 29 using a mixture of UAIH4 and Me3SiCl (Scheme 13).31 This procedure appears useful, as phosphinates of type RP(0)(0Et)2 are often robust compounds that can be prepared in a number of ways. (e.g. Michaelis-Arbusov reaction, palladium-catalysed coupling of diethyl phosphite with aryl bromides, etc.)... 

Another heterobidentate chiral ligand that has been used with success in catalysis is the phosphine QUINAP , 90. It is prepared using a palladium-catalysed coupling procedure, followed by a resolution of the racemic product using a chiral palladium salt (Scheme 32).58... 

One of the most elegant methods for the preparation of phosphinine proceeds through and intermediately formed trihalophosphacycloalkene (Scheme 5). When (dihalomethyl)dihalophosphines are heated with reactive dienes (e.g. alkyl-substituted buta-1,3-dienes) in the presence of excess triethylamine, the corresponding 2-halophosphinine is obtained in a simple, one-pot reaction.39,40 2-Bromophosphinine is of particular interest because it readily participates, for example, in palladium-catalysed coupling reactions.41... 

NMR experiments on the reactions of halophosphates esters with pyridine showed that equilibria involving the formation of pyridinium salts in these reactions are almost entirely shifted to the left for chloro- and bromo-phosphates and to the right for the corresponding iodophosphates. This explains dramatic differences in chemical reactivity between these compounds. Substituted medium-sized and large N-heterocycles (117) have been prepared via an extension of the Suzuki reaction involving the palladium-catalysed coupling of vinyl-phosphates (118) with aryl or heteroaryl boronic acids (Scheme 27). ... 

A two step synthesis of 2-oxo-2-vinyl-l,3,2-dioxaphospholanes and dioxa-phosphorinane (392) involves transesterification of diethyl phosphite with selected diols followed by palladium catalysed coupling of the resultant cyclic phosphites (393) with vinyl bromide (Figure 67). ... 

Frost, C. G. Palladium catalysed coupling reactions, in Rodd s Chemistry of Caiton Compounds (2nd Edition) 5, 315-350 (Elsevier, Amsterdam, New York, 2001). 

Alkynylstannanes react with copper(II) nitrate to give, via the alkynylcopper(II) derivatives, the corresponding 1,3-dialkynes108 and they show a high reactivity in Stille-type palladium-catalysed coupling reactions (Section 22.2).109... 

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