Palladium containing derivative

Reaction of the cyclometallated derivative of phenyl-2-pyridylketone 73 leads to indenol-chelated, palladium-containing derivatives 74. Here, incorporating an electrophilic (CO) function in the starting palladacycle signifies that, following alkyne insertion in the Pd-C bond, an intramolecular attack of the vinyl palladated unit on the metal-bound, activated CO function occurs. This is in sharp contrast to the reaction described in Scheme 9 whereby incorporating a nucleophilic, masked, secondary amine function leads to indole derivatives 40 and to the azepinium synthesis from the metallated benzylpyridine complex 34. Therefore, these reactions are rather sensitive to the nature of other potentially reactive functions within the metallacyclic framework. 

The aim of this account was to show that cyclometallated complexes, the majority being palladium-containing derivatives, in stoichiometric or catalytic quantities, can certainly be part of the arsenal of the chemist seeking to synthesize cyclic compounds selectively and efficiently. One of the major themes of our research in this respect has been to study these reactions from an organometallic chemist s point of view, with the particular goal of defining the precise role of the metal in the hetero- or carbocyclization process. This has led to some unusual and fruitful mechanistic findings and some useful synthetic approaches to many novel hetero- and carbocyclic systems. 

This operation effectively removes the remaining palladium-containing compounds, phosphine derivatives, and borane residues. 

Some of the earliest attempts to prepare dehydrocorrin derivatives used a tetrapyrrole compound already containing a direct linkage between the two central rings. When its palladium(Il) derivative was treated with formaldehyde and hydrochloric acid it underwent cyclization but with the insertion of an oxygen atom rather than the desired carbon bridge (equation 51).261 Subsequent treatment of the same starting material with ammonia, methylamine or sodium sulfide gave rise to related macrocyclic products. 

FIGURE 24 Generation of supramolecular catalysts for allylic amination (89) (A) assembly of pseudoenantiomeric bisoxazoline derivatives. CAChe-minimized model of the palladium-containing supramolecular complex and (B) palladium-mediated enan-tioselective allylic amination. (See Color Insert in the back of this book.)... 

As is seen from discussion above, the vast majority of Mizoroki-Heck reactions belong to either type 1 or type 2 processes, which involve palladium with undefined coordination shells. In the presence of halide ions (liberated during the reaction or derived from additives) and anionic bases, the coordination shell of palladium contains as many anionic ligands as it can pos sibly bear [32]. Thus, these catalyses do only pass through coordination equilibria involving charged reactants on both sides. Similar considerations apply to typed systems, which involve cationic intermediates. 

Insertion of palladium vinyls derived from 30 into tethered alkynes leads to 31. In the presence of alkenes, or appropriate pendant unsaturated functions, rearrangemrat to 32 and spontaneous cyclisation take place. These reactions therefore constitute efficient routes to arene or diene > containing, or completely saturated - tricyclic systems under PdL2 catalysis. If the geometry of 32 is unfavourable or prevented completely diverse products can arise, including cyclopropanes. 52... 

Other interests involve the use of palladium-containing compounds themselves in nonbiological applications. For instance, the products derived from the condensation of KpPdCl. with polyvinyl pyridine form materials with low threshold voltages for imagining and high-speed recording (2). Flexible, electrically conductive films have been prepared from the reaction of K PdCli with polyimides (3). 

As with homopolymers, block copolymers may incorporate metals such as in the work of Chan and Schrock where palladium-containing norbornene moieties were copolymerized and the metal reduced below the Tg of the polymer to afford metal clusters whose size was modulated by the polymeric composition. Even with fairly labile metals, the gentle reaction conditions of ROMP can incorporate them into polymeric networks. The ROMP of a variety of norbornene derivatives bearing cationic iron moieties was accomplished without loss of the iron, whereas heating above 100 °C resulted in loss of the iron without degradation of the polymer. The norbornene polymer sans iron was also realized via photolysis. ... 

Formic acid behaves differently. The expected octadienyl formate is not formed. The reaction of butadiene carried out in formic acid and triethylamine affords 1,7-octadiene (41) as the major product and 1,6-octadiene as a minor product[41-43], Formic acid is a hydride source. It is known that the Pd hydride formed from palladium formate attacks the substituted side of tt-allylpalladium to form the terminal alkene[44] (see Section 2.8). The reductive dimerization of isoprene in formic acid in the presence of Et3N using tri(i)-tolyl)phosphine at room temperature afforded a mixture of dimers in 87% yield, which contained 71% of the head-to-tail dimers 42a and 42b. The mixture was treated with concentrated HCl to give an easily separable chloro derivative 43. By this means, a- and d-citronellol (44 and 45) were pre-pared[45]. 

Reductive cleavage of phenylhydrazones of carbonyl compounds provides a route to amines. The reduction is carried out conveniently in ethanol containing ammonia over palladium-on-carbon. Ammonia is used to minimize formation of secondary amines, derived by addition of the initially formed amine to the starting material (160). Alternatively, a two-phase system of benzene, cyclohexane, toluene, or dioxane and aqueous hydrochloric acid can be used. 

Non-ionic thiourea derivatives have been used as ligands for metal complexes [63,64] as well as anionic thioureas and, in both cases, coordination in metal clusters has also been described [65,66]. Examples of mononuclear complexes of simple alkyl- or aryl-substituted thiourea monoanions, containing N,S-chelating ligands (Scheme 11), have been reported for rhodium(III) [67,68], iridium and many other transition metals, such as chromium(III), technetium(III), rhenium(V), aluminium, ruthenium, osmium, platinum [69] and palladium [70]. Many complexes with N,S-chelating monothioureas were prepared with two triphenylphosphines as substituents. 

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