Amines palladium catalysed reactions

Carbon-carbon bond formation reactions and the CH activation of methane are another example where NHC complexes have been used successfully in catalytic applications. Palladium-catalysed reactions include Heck-type reactions, especially the Mizoroki-Heck reaction itself [171-175], and various cross-coupling reactions [176-182]. They have also been found useful for related reactions like the Sonogashira coupling [183-185] or the Buchwald-Hartwig amination [186-189]. The reactions are similar concerning the first step of the catalytic cycle, the oxidative addition of aryl halides to palladium(O) species. This is facilitated by electron-donating substituents and therefore the development of highly active catalysts has focussed on NHC complexes. 

A number of palladium-catalysed reactions of the triflate 61 have been reported but the nucleophilic displacement with primary aliphatic amines was, surprisingly, very slow in refluxing THF (24-92h). However, under microwave irradiation the reactions were very rapid and gave high yields, although even with microwaves, secondary amines and anilines failed to... 

G-Allylic urethanes and carbonates are afforded from amines/alcohols, carbon dioxide and allylic chlorides by palladium catalysed reaction in the presence of an organobase. The choice of added base in the generation of carbamates/carbonates was critical for high yields... 

The use of transition-metal catalysts in the substitution of aryl halides by amines has been reviewed. There has also been a summary of the use of palladium catalysts in the reaction of aryl and heteroaryl halides with primary and secondary amines. It has been shown that the amination of aryl sulfamates by aliphatic amines may be achieved using a nickel catalyst with an A-heterocyclic carbene ligand. Suitable ligands for nickel and palladium in the catalysed amination reactions of aryl sulfamates and imidazolylsulfonates have been identified. " The palladium-catalysed reaction of aryl nonafluorobutanesulfonates with primary sulfonamides may yield substituted products such as (22). Kinetic data suggest that reductive elimination from the palladium intermediate is likely to be rate limiting. A-Arylmethanesulfonamides may also be formed from aryl bromides and chlorides using a palladium catalyst... 

In the palladium-catalysed reaction of phthalimides with mono-, di-, and tri-substituted arenes lacking a DG, it has been shown that steric effects were dominant with ort/io-aminated products being disfavoured.The reaction of arenes with N-tosyloxytrichloroethyl carbamates is catalysed by copper with a neocuproine ligand and yields amidated derivatives. Reaction is faster with electron-rich arenes and the kinetic isotope effect, value of 0.9. The suggested mechanism involves... 

The coupling of anilines with arylboronic acids has been described in a process catalysed by palladium acetate without the need for ligands, bases, or salts. The mechanism shown in Scheme 17, where S represents solvent, involves in situ formation of the dia-zonium salt from the aniline, and formation of an arylpalladium alkoxo complex which allows the transmetallation step with arylboronic acids. It has been shown that a free amine may be used as a DG in a palladium-catalysed reaction promoted by soluble silver salts. The latter aid the formation of intermediates, (136), which may undergo cyclopalladation followed by transmetallation with an arylboronic acid and reductive elimination. Related work has shown thatbiaryl-2-amines may react with aryl iodides in the presence of palladium acetate and silver acetate to give mono- or di-arylated species such as (137). 

The palladium-catalysed reaction of vinylic halides with alkenes to form carbonyl compounds can be useful synthetically. Acrolein acetals can act as substrates in the presence of amines to form dienals in protected form [equation (34)].Addition of terminal vinylic iodides to enones is also possible,... 

Butadiene reacts with primary or secondary amines (/.e., R R NH) in the presence of [Pd(acac)2]+PPh3 to give 94% CH2=CH(CH2)3CH=CHCH2-NR R. Similar palladium-catalysed reactions of isoprene with diethyl-amine and isoprene with 3,3-dimethyldiaziridine, Me2CN(H)NH, have been reported. In the presence of traces of water, Pd(OAc)2+3.5 PPh3 catalyses reaction (22) the catalyst also isomerizes (23) to (22). ... 

Although one of the more recent additions to the armamentarium of these palladium-catalysed reactions, the Buchwald-Hartwig cross-coupling of amines with aiyl halides already has found applications in macrocycle synthesis. In the first example, Iqbal et al used this coupling as the cyclization step in the synthesis of constrained tri- or tetra-peptidomimetics with a biaiyl linker (Scheme 11.13 illustrates a tripeptidomimetic (112)). Fair to moderate yields were obtained for products containing 16- to 22-membered rings. 

The two diasteromeric allyliridium-phosphoramidite complexes formed in the allylic 5 2 substitution of /-substituted allylic acetates, benzoates, or carbonates, with amine nucleophiles have been synthesized and characterized by NMR and X-ray diffractions. Kinetic and stereochemical studies using deuterated substrates indicate that the reaction, which occurs with a retention of configuration, proceeds by the mechanism in Scheme 3. This iridium-catalysed reaction is compared to molybdenum- and palladium-catalysed reactions. 

The secondary amide can also attack intramolecularly an additional ester function to form a cyclic imide, although only in moderate yields [67], Finally, the palladium-catalysed intramolecular reaction with an alkyne, resulting in a hydro-amination of the latter, will be described later (Fig. 17) [68]. 

The palladium catalysed formation of indole derivatives has been extended by Grigg, who used carbon monoxide and unsaturated amines to trap the palladium complex formed in the insertion step. Reaction 3.10. provides an example of such a transformation. The amides were converted to the cyclic derivatives using ring closing metathesis.13... 

Not only acetylene derivatives do undergo palladium catalysed intarmolecular carbon-nitrogen bond formation with amines. The similar reaction of olefins in a Wacker-type process also leads to ring closure. (0-Aminopentenes bearing a suitable leaving group in the 4-position were converted to pyrroles in a cyclization-isomerisation-elimination sequence (3.65.),82... 

The silver(I) complexes of the furan functionalised bis-carbene ligands were used for the palladium catalysed aryl amination of p-bromotoluene with morpholine as the amine and [Pd(dba)j] as the precatalyst employing an in situ protocol. Performance of the catalyst was poor, but increased somewhat with additional bulk on the wingtip groups (Me < Bu < Mes) and the reaction time. The latter indicates that the catalyst, formed in situ, is stable under catalytic conditions and remains active over prolonged reaction times. 

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