Alkylation metal-free

The preparation of a novel pentadentate ligand, 2-hydroxy-5-methylisophthalalde-hyde bis(/7-methoxy thiobenzoylhydra-zone), was described together with the chloro-bridged Zn(II) complexes [127]. Synthesis and electrochemical properties of some long-chain 1,4,8,11,15,18,22,25-octa-alkylated metal-free and zinc phtha-locyanines were presented by Swarts et al. [128]. The zinc derivatives show higher Kquid crystalline behavior than the free-metal compounds. 

Metallocorroles (M = Cu, Ni or Pd) can also be alkylated under the same conditions as the metal-free corroles23,24 to give the N2i-alkylated products together with a small amount of C3 alkylated product ( f = Pd). Allyl halides or bulky alkyl halides react with nickel corroles also at the 3-position. 

Figure 29. For the latter case, it is considered that the semiconducting re-electron systems are separated by insulating hydrocarbon spacers, resulting in alternate thin layers of organic semiconductor and insulator in these monolayer assemblies. The direct current - voltage (I - V) characteristics were mea- sured for the multilayers H2Pc(R)8 and Cu-Pc(R)8 in directions perpendicular and parallel to the film plane. In both cases, the linear I - V relationships of Ohm s law were observed at low electric field and obtained DC conductivities are summarized in Table 3. The normal conductivity (ajJ were ca. 10 13 S cm-1, while the lateral ones p//) were 3.4 x 10-7 and 9.9 x 10 7 S cm 1 for films of the metal-free and copper Pc derivatives, respectively. The former (ojJ tended to decrease slightly with increase of Figure 29. Schematical illustration of the substituent alkyl chain length,...

The Ge-Ge bond can undergo cleavage in reactions with [Bu4N]F to yield metal-free germyl anions, which can be employed in subsequent reactions with alkyl halides (Equation (210), Table 27) and carbonyl species (Equation (211), Table 28).266... 

There is ample evidence that the reductive elimination of alkanes (and the reverse) is a not single-step process, but involves a o-alkane complex as the intermediate. Thus, looking at the kinetics, reductive elimination and oxidative addition do not correspond to the elementary steps. These terms were introduced at a point in time when o-alkane complexes were unknown, and therefore new terms have been introduced by Jones to describe the mechanism and the kinetics of the reaction [5], The reaction of the o-alkane complex to the hydride-alkyl metal complex is called reductive cleavage and its reverse is called oxidative coupling. The second part of the scheme involves the association of alkane and metal and the dissociation of the o-alkane complex to unsaturated metal and free alkane. The intermediacy of o-alkane complexes can be seen for instance from the intramolecular exchange of isotopes in D-M-CH3 to the more stable H-M-CH2D prior to loss of CH3D. 

Yonker, C. R. and Linehan, J. C., A high-pressure NMR investigation of reaction chemistries in a simple salt hydrate,. Supercrit. Fluids, 29, 257 2004. Mehnert, C. R, Supported ionic liquid catalysis, Chem. Eur. ]., 11,50,2005. Giernoth, R. and Bankmann, D., Transition-metal free synthesis of perdeuter-ated imidazolium ionic liquidsby alkylation and H/D exchange, Eur. J. Org. Chem., 2008 (in print). DOT 10.1002/ejoc.200700784. 

The metal-free eyclobutane-1,2-dioxime can be generated by oxidative displacement. It is interesting to note that, unlike ketene dimerization, head-to-head dimerization takes place here. The chromium ketenimine complex 20 is prepared by reaction of the Fischer-type chromium carbene complex with alkyl isocyanides.60 A cyclobutane-1,2,3,4-tetraimine 24 has been reported from the reaction of the ketenimine phosphonium ylide 22.61 Bisimine 23 has been proposed as the intermediate in this transformation. 

Porphyrins have four inner nitrogens and show four stepwise add-base reactions (equation l).14 The pX, and pK2 values are estimated to be 16, pX3 is 5, and pX4 is 2 for /J-alkylated porphyrins. Because of N protonation, electrophilic meso deuteration of metal-free porphyrins is slower in strong acids (H2OEP in TFA-d, T,/2 = 275h at 90 °C) than in weak acids (t1/2 = 140 + 14 min in refluxing AcOD).2 Metalloporphyrins are more easily deuterated in strongly acidic media, e.g. M(OEP) (M = Fe, Cu, Pt) are completely meso-deuterated in TFA- CDC (1 1) at room temperature within 20 min. Meso deuteration of M(OEP) is possible under basic conditions (Mgl2-D20 or MeOD-hot pyridine).2... 

Akopova reported liquid crystalline phthalocyanines 116ac (Scheme 63) with eight peripheral crown ethers devoid of alkyl chains [132]. Nonetheless, discotic nematic phases could be observed as derived from miscibility experiments with the discotic nematogen hexa(cyclohexanebenzoyloxy)triphenylene and optical textures. In the case of metal-free 116a, a phase width of 43 K was found. Complexation with Zn(II) (116b) decreased the phase range to 35 K and with... 

A mandelamide diastereomer catalyses addition of both aryl- and alkyl-zincs to heteroaromatic aldehydes in high yield and ee, giving heterocyclic propargyl alcohols, under otherwise metal-free conditions 228... 

As mentioned above, reactions of this type have been widely used in the synthesis of macrocyclic ligands. Indeed, some of the earliest examples of templated ligand synthesis involve thiolate alkylations. Many of the most important uses of metal thiolate complexes in these syntheses utilise the reduced nucleophilicity of a co-ordinated thiolate ligand. The lower reactivity results in increased selectivity and more controllable reactions. This is exemplified in the formation of an A -donor ligand by the condensation of biacetyl with the nickel(n) complex of 2-aminoethanethiol (Fig. 5-78). The electrophilic carbonyl reacts specifically with the co-ordinated amine, to give a complex of a new diimine ligand. The beauty of this reaction is that the free ligand cannot be prepared in a metal-free reac-... 

A procedure for alkylation of C=0 double bonds in the presence of (metal-free) organocatalysts and non-metallic nucleophiles has been reported by the Iseki group for trifluoromethylation of aldehydes and ketones [185]. On the basis of a previous study of the Olah group [186, 187] which showed the suitability of non-chiral phase-transfer catalysts for trifluoromethylation of carbonyl compounds, Iseki et al. investigated the use of N-benzylcinchonium fluoride, 182, as a chiral catalyst. The reaction has been investigated with several aldehydes and aromatic ketones. Trifluoromethyltrimethylsilane, 181, was used as nucleophile. The reaction was, typically, performed at —78 °C with a catalytic amount (10-20 mol%) of 182, followed by subsequent hydrolysis of the siloxy compound and formation of the desired alcohols of type 183 (Scheme 6.82). 

The reaction between (por)nFe or (porT)uFe- and RX [Eq. (13.14) or (13.18)] obeys the relation of Eq. (13.20), and is more complete as the value of (—AGreac) is more positive. Therefore, the lower and upper limits of the free energy for bond formation (—AGBF) in a-alkyl-metal (Fe or Co) porphyrins are given by the relations... 

In summary, the electrochemical results indicate that the alkyl-metal bond-formation free energies range from 54 to 146 kJ mol-1 for iron porphyrins and from 84 to 159 kJ mol-1 for cobalt porphyrins. The maximum bond energies are for primary alkyl groups bonded to [(MeO)4TPP]Con and (OEP)Fen porphyrins. The porphyrin dianions [(porT)nFe and (porr)nCo ] facilitate the reduction of C02 to CO via the transient formation of a metal-carbon bond [(por7)M—C(0)0- — AGBF > 50 kJ mol-1 for iron porphyrins]. Thus, iron and cobalt porphyrins are especially effective electrocatalysts for the reduction of C02 ... 

The photochemical alkylation of olefins by nitriles and ketones is not straightforward, due mainly to the inefficient abstraction of hydrogen from an electron-withdrawing-substituted carbon by an electrophile such as the photocatalyst excited state. Nevertheless, various methyl ketones have been synthesized by the irradiation of a ketone/oleftn mixture dissolved in aqueous acetone. The mechanism of the reaction remains to be clarified, but a water-assisted C—C coupling between an acetonyl radical and the olefin has been postulated (Scheme 3.12). The reaction has several advantages, as it is cheap (an acetone/water mixture is used as the solvent) and occurs under mild metal-free conditions with no need for a photocatalyst [28],... 

Dichiarante, V., Fagnoni, M. and Albini, A. (2007) Metal-free synthesis of sterically crowded biphenyl by direct Ar-H substitution in alkyl benzenes. Angewandte Chemie, International Edition, 46, 6495-6498. 

Biocidal applications. The use of quaternary ammonium salts in disinfecting systems for household and industrial cleaners has been known for many years [95, 96]. Alkyl-benzyldimethyl quaternaries, alkyltrimethyl quaternaries, and dialkyldimethyl quaternaries are the more commonly used biocidal quaternary ammonium salts [16]. Recently, dialkyldimethyl quaternary ammonium salts have received renewed attention as potential wood preservatives to replace the heavy metal types [97]. Metal-free wood preservative formulations containing dialkyldimethyl ammonium salts with non-halide anions, such as carboxylates, borates, and carbonates, have been developed [98, 99]. 

Reaction between a reducing alkyl metal compound and a transition metal compound proceeds through a series of alkylated transition metal compounds which can decompose into lower valent transition metal compounds and free radicals (284, 289, 318—332). 

The synthesis of aza-oxa crown ethers is best accomplished by making carbon-nitrogen bonds in the cyclisation step. Although the original syntheses operated under conditions of high dilution and involved the co-condensation of a diamine with a diacid chloride, these methods have been supplanted by the more versatile and convenient A-alkylation pathways involving toluene-sulfonamide or TV-benzyl intermediates. This chapter has focused on the metal-free synthesis of saturated aza-oxa crown ethers. There are a large number of examples of the synthesis of aromatic and heterocyclic aza-oxa crown ethers that involve the co-condensation of aldehydes and amines mediated by metal ions such as Pb2+ and Ba2+24,25 This in situ synthetic... 

MFI zeolites seem to be the most efficient for EB dealkylation, in terms of activity, selectivity and stability. In the 70s, on metal-free MFI catalysts, EB was disproportionated into benzene and diethylbenzenes. As indicated above, with MFI catalysts, ethylbenzene disproportionation occurs through a deethylation-ethylation mechanism, with ethylene as desorbed intermediate. The addition of a metal (carried out early 80s) allows a rapid and irreversible conversion of ethylene into ethane with a consequent shift of ethylbenzene transformation from disproportionation to hydrodealkylation. The selectivity is highly sensitive to temperature that must be in the range 380°C-460°C to limit both alkylation and naphthene cracking. 

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