Heck-type, palladium acetate

Compounds similar to the above may also be obtained by an intramolecular Heck-type reaction of the bromo compound 103. Treatment of 103 with palladium(ll) acetate gives a mixture of two isomers, of which the major is 104 (with the more extended conjugation) (Equation 20) <1995JOC2312>. 

Heck reaction of 5-iodo-2,4-dimethoxypyrimidine and the furanose 3-deoxyglycal 147 with catalytic quantities of palladium acetate gives a mixture of the 2,3- and 3,4-enes 148 and 149 (Scheme 15). With triphenylarsine also present the latter product is favored, whereas with triphenylphosphine the 2-ene is produced without its isomer.164 Further examples of this type of chemistry have been reviewed by Daves.118... 

Heck-type vinylations of alkynic halides proceed only under solid-liquid phase-transfer conditions. These mild conditions allow the reaction to be performed with thermily unstable substrates. Thus, methyl ( )-enynoates can be obtained from the reaction of 1-iodoalkynes with methyl 2-propenoate in DMF at room temperature in the presence of potassium carbonate, tetrabutylammonium chloride and a catalytic amount of palladium acetate (Scheme 36)." ... 

Reaction of organic halides with alkenes catalyzed by palladium compounds (Heck type reaction) is known to be a useful method for carbon-carbon bond formation at unsubstituted vinylic positions. The first reports of the application of MW methodology to this type of reaction were published by Hallberg et al. in 1996 [109] and by Diaz-Ortiz et al. in 1997 [llOj both used in triethylamine solutions. Later, Ville-min et al. studied the possibility of Heck coupling of iodoarenes with methyl acrylate in aqueous solution under pressurized conditions [111]. The reactions were conducted in a Teflon autoclave under the action of MW irradiation in the presence of palladium acetate, different phosphine ligands, and tetrabutylammonium hydrogen sulfate (TBAHS) as PTC catalyst, to afford the desired coupling products in 40 to 90% yield. 

Scheme 1.7 Formation of Pd-carbene complexes by reaction between palladium acetate and imidazolium salts followed by decomplexation at high temperature and formation of catalytically active PdNPs for Heck-type reactions [33e,i,jj.

Heck-type reactions with enol carboxylates (e.g., vinyl acetate) are generally complex. Most common are reactions in which vinyl acetate is employed as an ethylene equivalent (see Scheme 24). However, an example of a preparatively useful reaction with an intact acetate function is given in entry 44.The reaction of vinyl triflates with vinyl phosphonates affords the corresponding conjugate dienylphosphonates (entry 45).f A new access to reactive nonaflates via a one-pot nonaflation-Heck reaction was recently reported (entry 46). " This reaction sequence starts from silyl enol ethers and provides functionalized 1,3-dienes in a simple manner, lodonium salts can be used as RPd precursors (entry 47). It is notable that the palladium(O) insertion preferentially occurs inbetween the iodonium ion and the vinylic, rather than the arylic sp -hybridized carbon (entry 47). Some years ago, Jeffery used acetylenic halides to achieve (JiJ-enynoates and (Ji)-enynones in fair yields at room temperature (entry 48). ... 

Palladium acetate immobilized on reversed-phase amorphous silica gel with the aid of an ionic liquid, [BMIm] PFs, was highly efficient in Mizoroki-Heck type reactions in water under ligand-free conditions. In several runs (up to the sixth reuse) a 95% average yield was obtained with a turnover number (TON, the number of converted substrate molecules per catalytically active centre, mol x mol ) of 1600000 and a turnover frequency (TOP, TON per time unit, mol x mol x h ) of 71000h [34]. 

The first palladium-catalyzed carbonylations of aryl halides were published in 1974 and 1975 (Equation 17.59). ° Heck first reported the synthesis of benzoates by the reaction of an aryl iodide, carbon monoxide, and an alcohol in the presence of a tertiary amine and catalytic amoimts of the combination of palladium acetate and triphenylphosphine. Concurrently, he reported the synthesis of benzamides from an aryl iodide, carbon monoxide, a primary amine, and a tertiary amine as base catalyzed by the same type of palladium complex. The related reactions of vinyl halides were also reported, and these reactions occurred with retention of the olefin geometry. ... 

In similar Heck-type reactions, commercially available palladium acetate is used as a catalyst, providing a new route for synthesizing indoles, benzofurans, 1,2-dihydroisoquinolines and other interesting derivatives, quite gratifyingly with regioselectivities often matching those reported in our chemistry. ... 

An intramolecular Pd-mediated Heck-type approach to 3-pyrrolin-2-ones has been disclosed by Yang and Shea (1995MI1 Scheme 30). Treatment of N-allyl-2-bromoacetamide 152 with palladium acetate and triphenylphos-phine in acetonitrile gives 4-methyl-3-pyrrolin-2-one 153 by a 5-exo-trig cyclization onto a terminal alkene, reductive elimination, and isomerization... 

The Sasai research group found an intramolecular Heck-type approach to simple 3-pyrrolin-2-ones (Scheme 50 2010CC9064). For example, treatment of P,y-unsaturated amide 218 with palladium acetate in the presence of the isoxazoline ligand 219 and p-benzoquinone gives 3-pyrroUn-2-one 220 via a S-endo-trig cyclization. 

A Heck-type CDC reaction of indolizines with electron-deficient alkenes produces 3-alkenyl-substituted indolizines. The reaction took place selectively at the 3-position through palladium(II)-catalysed C-H activation, following a Heck-type cross-coupling reaction under mild and ligand-free conditions. The results of the H/D exchange experiments confirmed that the C-H activation was catalysed by palladium(II) acetate (Scheme 8). ... 

A Leimbruger-Batcho-type amino-enamine intermediate is likely to be involved on reduction of the base-catalysed condensation product of an ortho-nitro araldehydes with nitromethane. Reduction, traditionally with metal/acid combinations, but now with reagents such as palladium/carbon with ammonium formate and formic acid, iron with acetic acid and silica gel, or titanium(III) chloride, gives the indole. The arylacetaldehyde precursors can also be generated by Heck reactions on vinylidene carbonate. ... 

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