Azobenzenes palladium complexes

Carbon monoxide insertion is another widely observed reaction. The following carbon monoxide insertion into an azobenzene palladium complex is typical lu). Azobenzene-palladium chloride complex has a carbon-palladium bond at the ortho-position, the carbonylation of which gives indazolinones by carbon monoxide insertion. Further carbonylation of indazolinone catalyzed by Co2(CO)8 produces quinazolinedione, hydolysis of which gives aniline and anthranilic acid 172). Thus this method is useful for the synthesis of substituted anthranilic acid. 

NjChHh, 1,2-Ethanediamine, N,N,N, N -tetramethyl-lithium complex, 26 148 NjCmH, 2,2 -Bypyridine rhenium complexes, 26 82, 83 N2C, H, Azobenzene cobalt and palladium complexes, 26 175, 176... 

C12H111N2, Azobenzene, cobalt and palladium complexes, 26 175, 176 manganese complex, 26 173 C12H11N, Pyridine, 2-(phenylmethyl)-, palladium complex, 26 208-210 C12H11P, Phosphine, diphenyl-, manganese complex, 26 158, 226-230 ruthenium complex, 26 264 Ci2H,20,S, Thiophenetetracarboxylic acid, tetramethyl ester, 26 166 C 2H,5N, Naphthalenamine, A ,iV-dimethyl-, lithium complex, 26 154 Cj2Hih, Benzene, hexamethyl-, ruthenium complex, 26 181, 182... 

One of the earlier contributions to the revival of metal-containing liquid crystal systems was the synthesis of the ort, ti-metallated palladium complexes of mesogenic azobenzenes 91, 92 by Ghedini and co-workers, which represented the first systematic attempt to coordinate metals to known liquid-crystal systems. 

N2C,2H,q, Azobenzene, cobalt and palladium complexes, 26 175,176 manganese complex, 26 173 NjClPdC,, Palladium(Il), chloro[2-(2-pyridinylmethyl)phenyl-C 2Vl(3,5-dimethylpyridine)-, 26 210 N2CI2P2CJH1J, 1,3,2,4,-Diazadiphospheti-dine, l,3-di-terr-butyl-2,4-dichloro-, cis-, 27 258... 

In some of the preceding examples a molecule of CO (a one-carbon unit) has formally inserted into the M-C other examples of this type of reaction, which affords heterocycles, have been described, using, for example, palladium complexes (Takahashi and Tsuji, 1967) or octacarbonyl dicobalt as a catalyst and azobenzenes, Schiff bases, oximes, phenylhydrazones, semicarbazones, or azines as substrates (Mura-... 

Again such complexes are more prevalent in palladium chemistry. Examples in platinum(II) chemistry are found with azobenzene, 121< 1216 N,A-dialkylbenzylamine,1217 benzoquin-oline,1218 8-methylquinoline,1218 acetophenone oxime1220 and N-alky 1-7V-nit rosoanilines.1221... 

Diazocine 8 was found to form complexes very slowly or not at all with palladium chloride or silver nitrate. ( )-Azobenzene behaved similarly, and since both compounds have similar pXa values, the ease of complex... 

The formation of ortho palladium products from a-aryl nitrogen derivatives and palladium salts is well known. Complexes formed from azobenzene, Schiff bases, tertiary benzylamines and oximes readily undergo insertion of CO into the metal-carbon bond to give, after work-up, a variety of heterocyclic compounds. Unfortunately, such reactions use expensive palladium salts in stoichiometric quantities. However, a number of related reactions have been shown to proceed in the presence of only catalytic quantities of palladium. Isoindolinones, for example, can be synthesized in good yield by reaction of o-bromoaminoalkylbenzenes with CO (100 C, 1 bar) in the presence of catalytic amounts of Pd(OAc)2, PPha and Bu"3N (equation 56). °... 

A related series of palladium(II) azobenzene complexes with halogen bridging ligands has been prepared by Ghedini, in which the chirality was present in one of... 

An aromatic nitro function hydrogenates to the corresponding amine in high yield over palladium-on-carbon in a process that is slightly superior to that using platinum. Homogeneous reduction of aromatic compounds (1) by a triphenylphosphine complex of palladium yields anilines 2 along with minor quantities of azobenzene and azoxyben-zene derivatives . 

By palladium (O)-catalyzed carbonylation of l,2-diaza-l,3-buta-dienes. Boeckman et al. (01OL3651) (Scheme 42) reported that stable l-(l,2-diphenylethenyl)-2-phenyldiazene 180 when treated with 10 or 1 mol% of Pd(Ph3P)4 or Pd(dppe)2 catalysts, respectively, in toluene under 1 or 2 atm of carbon monoxide, at room temperature or 100 °C for 0.25-30 h, afforded pyrazol-3-one 184 in excellent yields. Although no intermediates were detected, by analogy to the previously studied cyclopalladation of azobenzene, the mechanism shown in Scheme 42 was proposed. The mechanism involves formation of a cr-complex 181 between 180 and Pd(0)-catalyst, cycloaddition by n—>-n isomerization to... 

The reaction of chlorine with the azobenzene complex affords ortho-chlorinated azobenzene, and palladium chloride is regenerated 112). 

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