Cyclopalladated

The asymmetric cyclopalladation of dimethylaminomethylferrocene takes place in the presence of an optically active carboxylic acid (e.g, A -acetylvaline), giving the cyclopalladation product 478 in 78% ee, from which optically active ferrocene derivatives were prepared[434]. 

Oxygenation takes place with peracids. The cyclopalladated benzylamine complex 466 is converted into the salicylaldamine complex 504 by the treatment with MCPBA[456] or /-BuO H[457]. Similarly, azobenzene is oxidized with MCPBA at the ortho position[458]. 

The facile cyclopalladation of allylamine proceeds due to a chelating effect of the nitrogen. In MeOH, methoxypalladation take.s place to give the five-mem-bered chelating complex 507[460). The CO Insertion takes place readily in EtOH, giving ethyl 3-methoxy-4-dimethylaminobutyrate (508) in 50% yield[461). The insertion of alkenes also proceeds smoothly, giving the ami-noalkenes 509[462],... 

An unactivated methyl group can be functionalized by the cyclopalladation of oximes. The equatorial methyl of geminal methyls in steroids or hexapyr-anosides is selectively aceto.xylated by the reaction of the palladation complex 523 of the 3-oxime with lead tetraacetate[467,468]. 

The cyclopalladated complexes of hydrotiis(pyrazol-l-yl)borate and tetrakis (pyrazol- l-yl)borate have a common feature of bidentacy of the pyrazol- 1-ylborate... 

Organonickel derivatives also offer cases of the -coordination of the substituted hydrotrisfpyrazol- l-yl)borate ligand. For the palladium and platinum complexes, the M(II) M(IV) (M = Pd, Pt) transformation is facile. Organopalla-dium chemistry offers anew type of agostic interactions, C—H - - - Pd, where the C—H bond belongs to one of the pyrazolate rings. Cyclopalladation of various pyrazol-l-ylborates and -methanes does not modify their structure. 

TL2403). Thus, or /io-cyclopalladation of acetanilide 138 gave organo-palladium reagent 139. The or /io-vinylation of 139 afforded enone 140, which was then cyclized to quinoline 141 under acidic conditions. Notice this reaction requires stoichiometric amounts of Pd(OAc)2. 

Methylphenyl)benzothiazole (80IC762) and 2-benzylbenzothiazole (95ICA(239)125) can be cyclopalladated. In the latter case, cylopalladation occurs upon reaction with palladium(II) acetate and gives the product 80. With lithium chloride, sodium bromide, or sodium iodide, a series of three products of substitution of the acetate group 81 (X = C1, Br, I) results. Pyridine, 2- and 3-methylpyridine, 2,6- and 3,5-dimethylpyridine cause the transformation of the chelate complexes 81 (X = C1, Br, I) and formation of the mononuclear products 82 (R = z= R" = = R = H, X = Cl, Br, I ... 

Complexes of the nickel subgroup include C-coordinated, carbene, ring-opened, and cyclopalladated cases, while N-coordination is scarce. 

Hollis TK, Overman LE (1997) Cyclopalladated ferrocenyl amines as enantioselective catalysts for the rearrangement of allylic imidates to allylic amides. Tetrahedron Lett 38 8837-8840... 

Cohen F, Overman LE (1998) Planar-chiral cyclopalladated ferrocenyl amines and imines as enantioselective catalysts for allylic imidate rearrangements. Tetrahedron Asymmetry 9 3213-3222... 

Moyano A, Rosol M, Moreno RM, Lopez C, Maestro MA (2005) Oxazoline-mediated interannular cyclopalladation of ferrocene chiral palladium(II) catalysts for the enantioselective Azti-Claisen rearrangement. Angew Chem Int Ed 44 1865-1869... 

Jautze S, Diethelm S, Frey W, Peters R (2009) Diastereoselective bis-cyclopalladation of ferrocene-1,1 -diyl bis-imidazolines translation of central via axial into planar chirality. Organometallics 28 2001-2004... 

Photorefractivity is a property exhibited by some materials in which the redistribution in space of photogenerated charges will induce a nonuniform electric space-charge field which can, in turn, affect the refractive index of the material. In a new material the active species is a highly efficient cyclopalladated molecule97,98 shown in Figure 5. The palladium-bonded azobenzene molecule is conformationally locked, and gratings derived from cis—trans isomerizations can be safely excluded. 

Kostic el al. discovered that Pd11 complexes, when attached to tryptophan residues, can rapidly cleave peptides in acetone solutions to which a stoichiometric amount of water is added, for hydrolysis.436 The indole tautomer in which a hydrogen has moved from the nitrogen to C(3) is named indolenine. Its palladium(II) complexes that are coordinated via the nitrogen atom have been characterized by X-ray crystallography and spectroscopic methods.451 Binuclear dimeric complexes between palladium(II) and indole-3-acetate involve cyclopalladation.452 Bidentate coordination to palladium(II) through the N(l) and the C(2) atoms occurs in binuclear complexes.453 Reactions of palladium(II) complexes with indole-3-acetamide and its derivatives produced new complexes of unusual structure. Various NMR, UV, IR, and mass spectral analyses have revealed bidentate coordination via the indole carbon C(3) and the amide oxygen.437... 

Diastereomerically pure (2W,5.V)-l,3-diaza-2-(2-methylphenyl)-3-phenyl-2-phosphabicyclo[3.3.0]octane (.S )-202] was formed in the thermal reaction of (S)-2-(anilinomethyl)pyrrolidines (197a) with o-TolP(NMe2)2 and isolated in 27% yield after recrystallization (Scheme 56) [87], Its cyclopalladation with palladium diacetate followed by anion metathesis gave dimer (5,5)-203 (Scheme 56) [87],... 

The insertion of allenes in the Pd-C bond of cyclopalladated 3-arylisoquinoline derivatives 327 afforded compounds 328, derived from the berberinium cation (Scheme 71). This reaction takes place via the formation of an intermediate (r/ -allyOpalladium complex <2003JOM313>. This chemistry has been extended to the preparation of other cationic N-heterocycles, including naphtho[r+/ ]( uinolizinium derivatives <2004EJ01724>. 

The conversion of functionalized arenes as represented by the general formula 97, into isothiazolium compounds (99) has been achieved by the sequence shown in Scheme 117.180 From a synthetic viewpoint, transformation of cyclopalladated products into thiocyanate derivatives is more efficiently achieved using monomeric dithiocarbamato complexes (98) rather than dimeric compounds. The generation of analogous dithiolylium perchlorates by a related procedure is described later (see Section IV,H). 

Another palladium complex, namely, a six-membered cyclopalladate complex of 2-benzoyl pyridine, has also been used for the hydrogenation of polymers [77, 78]. Possible catalytic mechanisms for the hydrogenation of natural rubber [76] and NBR [77] catalyzed by these two complexes were proposed, but unfortunately the authors did not provide sufficient evidence to support their proposed mechanisms. 

Five-membered cyclopalladated rings of type 137 (Scheme 58) were synthesized and studied by spectroscopic methods. Their X-ray structures were analyzed in terms of deviations from planarity, and data were used for the calculation of two aromaticity indices, V and HOMA,179 which are in agreement with an aromatic structure. 

The asymmetric aza-Claisen rearrangement of allyl imidates, (86) (87), has been shown to be catalysed by homochiral cationic palladium(II) complexes, and a series of enantiopure cyclopalladated ferrocenyl amines and imines have been... 

The insertion of allenes in the palladium-carbon a bond of cyclopalladated pyridine derivative 295 (cf. 00CRV3067) affords stable, isolable (ry -allyl) palladium complexes (e.g., 296) (03JOM(687)313). The ideally located imine unit when depalladated reacts selectively with the allyl functionality to yield methylene morphanthridizinium salts 297a-c. 

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