Aniline catalysts, palladium complexes

Secondary amines can be added to certain nonactivated alkenes if palladium(II) complexes are used as catalysts The complexation lowers the electron density of the double bond, facilitating nucleophilic attack. Markovnikov orientation is observed and the addition is anti An intramolecular addition to an alkyne unit in the presence of a palladium compound, generated a tetrahydropyridine, and a related addition to an allene is known.Amines add to allenes in the presence of a catalytic amount of CuBr " or palladium compounds.Molybdenum complexes have also been used in the addition of aniline to alkenes. Reduction of nitro compounds in the presence of rhodium catalysts, in the presence of alkenes, CO and H2, leads to an amine unit adding to the alkene moiety. An intramolecular addition of an amine unit to an alkene to form a pyrrolidine was reported using a lanthanide reagent. 

With the exception of intramolecular amination reactions, all of the early aryl halide aminations were catalyzed by palladium complexes containing the sterically hindered P(o-tol)3. In papers published back-to-back in 1996, amination chemistry catalyzed by palladium complexes of DPPF and BINAP was reported.36,37 These catalysts allowed for the coupling of aryl bromides and iodides with primary alkyl amines, cyclic secondary amines, and anilines. 

All of these processes are of limited synthetic utility because of the requirement of the use of stoi chiometric amounts of palladium complexes. However, by judicious choice of reactants and condition the above-mentioned impediments to catalysis can be overcome. For example, an efficient palladium(II) catalyzed cyclization of o-allyl- and o-vinyl-anilines to indoles has been developed (equation 14).28 Be cause arylamines are -106 less basic than aliphatic amines, and because the cyclized product in thi system gave an enamine (indole) stabilized by aromatization, the problems of catalyst poisoning by sub strate or product were circumvented, and catalysis was successfully achieved. The system was quit tolerant of a variety of functional groups and was used to prepare indoloquinones in excellent yieli... 

Palladium(O) complexes containing P(o-C6H4Me)3 as ligand show low reactivity toward aryl triflates [95,96]. Thus, the original catalyst is not effective for the ami-nation of aryl triflates. However, palladium complexes with the chelating phosphines DPPF and BINAP are effective [97,98]. Selected animations of aryl triflates by aniline are shown in Eq. (9), and selected animations of aryl triflates by alkylamines in Eq. (10). 

The dibenzo- 1,5-oxazocine 540 was obtained, in nearly quantitative yield, via intramolecular carbonylation of ortho-substituted aniline 539 with 100 psi CO in the presence of recyclable palladium-complexed dendrimer on silica (Gl-Pd) as catalyst and diisopropylethylamine (DIPEA) (Equation 23) <2005JA14776>. 

Catalyst libraries for combinatorial screening of diimine-based nickel and palladium catalysts can be developed by attaching a diketone to a Merrifield resin, reacting with a variety of anilines in the presence of a dehydrating catalyst, and complexing with the metal (Scheme 25). After each variant is activated with MAO or borate salt, the 96-well microtiter plate is exposed to ethylene and polymerization activity is qualitatively determined by infrared imaging. 

Easily synthesized, highly active, yet air- and shelf-stable palladium complexes have added to the existing arsenal of cross-coupling catalysts. Well-defined [(NHC)PdCl2]2 complexes have been used in aryl amination of more economical and more difficult to activate aryl chlorides and amines/anilines in DME as solvent and potassium fcrf-amylate (KO Am) as base [77]. When... 

Reaction of aniline (304) and ethyl trifluoroacetoacetate (305) resulted in formation of 4-trifluoromethylquinolin-2-one (306) from which 2-brom-4-trifluoromethyl-quinoline (307) was synthesized further. Reaction of compound 307 with pyridines 308 at the presence of a palladium complex as the catalyst resulted in quinoline ligands 309 [185] (Scheme 88). 

A remarkable process was reported by Mori that forms aniline from dinitrogen (Equation (26)).106 Titanium nitrogen fixation complexes were generated from reactions of titanium tetrachloride or tetraisopropoxide, lithium metal, TMS chloride, and dinitrogen. These complexes generated a mixture of aryl and diarylamines in yields as high as 80% when treated with aryl halide and a palladium catalyst containing DPPF ... 

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