4-Chloro-2- phenol ligand

Perdenteration of the methylene hnker affords a relatively kinetically stable complex, which allows for the monitoring of exogenons snbstrate oxidations. When (7) is exposed to cold (-95 °C) acetone solntions of the lithium salts of para-substituted phenolates, clean conversion to the corresponding o-catechols is observed. Deuterium kinetic isotope effects (KIEs) for these hydroxylation reactions of 1.0 are observed, which is consistent with an electrophilic attack of the peroxo ligand on the arene ring. An electrophilic aromatic substitution is also consistent with the observation that lithium jo-methoxy-phenolate reacts substantially faster with (7) than lithium / -chloro-phenolate. Furthermore, a plot of observed reaction rates vs. / -chloro-phenolate concentration demonstrated that substrate coordination to the metal center is occurring prior to hydroxylation, and thus may be an important feature in these phenolate o-hydroxylation reactions. 

Figure 4. Schematic of electron transfer processes for 2,6-disubstituted phenol. The ligand groups are indicated as Am and the intermediate polymer chain segments as straight lines, (a) Hydroxo-bridged catalyst (b) chloro-bridged catalyst.

Pd-Catalyzed Displacement of the Remaining Chloro Atom on C2 by Phenols (Fig. 10).15 To a 10-ml flame-dried Schlenk flask with resin 61 (0.10 mmol, 1.0 equiv.) are added a phenol (0.50 mmol, 5.0 equiv.), Pd2(dba)3 (0.007 mmol, 0.07 equiv.), l,l -biphenyl-2-yl-[di-(tert-butyl)]-phosphine (phosphine ligand) (0.028 mmol, 0.28 equiv.), and K3P04 (0.70 mmol, 7.0 equiv.). The Schlenk flask is purged with Ar and charged with anhydrous toluene (1.0 ml). The reaction is heated to 80° under Ar. 

The conditions vary from case to case and need to be optimized accordingly. Solution-phase synthesized ligands are characterized by H-NMR, 13C-NMR, and mass spectroscopy, and further immobilized on a solid support (see Note 9 or step 7c). As an example, we describe the solution-phase synthesis of ApA, 4-[2-(4-chloro-6-phenylamino-[l,3,5]-triazin-2-ylamino)-ethyl]-phenol (Fig. 2B). 

Hartwig [9] et al. developed a novel ferrocene-based dialkyl-phosphine-ligand for this arylation 2-methoxy-4-methyl-phenol is arylated with 2-chloro-p-xylene in 81% yield [eq. (g)]. 

Ferrocene-based phosphine 24 is also an effective supporting ligand for the Pd-catalyzed condensation of chloroarenes and sodium ferf-butoxide [148]. The coupling of 2-chloro-para-xylene, followed by acid mediated cleavage of the ferf-butyl group, yielded the desired phenol in 71 % yield, Eq. (190). 

Vanadium(IV) forms complexes with charged carboxylate, aryloxide and alkoxide functionalities as well as the neutral carbonyl group. The steric crowding of the /-butoxides allowed structural characterization of the tetraalkoxide (96) by gas-phase electron diffraction.475 Vw phenoxide complexes derived from ligands such as 2-(dimethylaminomethyl)phenol and 4-chloro-2-[(dimethylamino)methyl]phenol are active as ethylene and propylene copolymerization agents 476 Complexes with silanoxides have been prepared by the oxidation of Vnl complexes.477... 

The complexes ML2, where M = Co, Cu, Ni, Zn HL = 2-hydroxy-5-(chloro/ nitro)-benzaldehyde[4-(3-methyl-3-mesitylcyclobutyl)-l,3-thiazol-2-yl]hydra-zone, give IR spectra indicating chelation of L through azomethine N and phenolate O atoms.509 Coordination of the 5-(2 -carboxyphenylazo)-8-hydro-xyquinoline to Co, Ni, Cu or U022+ via CN, N=N, COOH and OH was shown by IR spectroscopy.510 IR data for M(II) (=Co, Ni, Cu, Zn) complexes of A -salicyloyl-A"-/)-hydroxythiobenzohydrazide and related ligands show coordination by thiolato S, enolic O and two hydrazine N atoms.511... 

The catalytically active cationic complex is preformed by reaction of complex 12 with the strong acid HCIO4 the phenolic oxygen is protonated and the coordinative bond of the bidentate vanillin ligand to platinum is cleaved at this end. In contrast to the treatment of 12 with HCl, which gives an inactive chloro-platinum complex, the non-coordinating anion [0104] leaves a vacant coordination site on the central metal, thus rendering it catalytically active. 

The aryl r-butyl ether 15 and silyl ether 18, prepared by the Pd-catalyzed reaction, can be converted easily to phenols 16, and these reactions offer convenient synthetic methods for phenols 16 from aryl halides 14 and 17. Based on this reaction, the first synthesis of 4-chlorobenzofiiran (18c), which is difficult to synthesize by conventional methods, was carried out. Selective mono-r-butoxylation of 2,6-dichloroacetaldehyde dimethylacetal (18a) using P(r-Bu)3 as a ligand gave the r-butyl ether 18b, and subsequent treatment with aq. HCl afforded 4-chlorobenzofuran (18c) in 51 % overall yield. Further conversion of 18c to various 4-substituted benzofurans is possible by Pd-catalyzed substitutions of the 4-chloro group in 18c [6]. 

The formation of phenoxy radicals upon oxidation from substituted phenols has been studied by the ESR technique, using nitrosodurene as spin trap [52]. Chloro(5,10,15,20-tetraphenylporphyrinato)cobalt(III) and its Ti-cation radical were used to promote the reaction. The phenols studied reacted with the cation radical but some of them interacted only with the complex. The reaction is pictured as involving electron transfer from the phenolate, mediated by an axially coordinated chloro ligand. 

Benzene, alkyl subs, 85, 87, 89, 223 Benzene, bromo subs, 85 Benzene, chloro subs, 85, 87, 223, 293 Benzene, cyano subs, 88 Benzene, disubs (mixed ligands) 86, 89 Benzene, hydroxy subs (phenols) 85, 83, 84, 85... 

Steric and electronic effects have been investigated for the Cu(acac)2-catalysed asymmetric oxidation of aryl benzyl, aryl alkyl and alkyl benzyl sulfides with H2O2 in presence of hexane/MeOH and the ligand 4-chloro-2-[( )-[( 17 )-l-(hydroxymethyl)-2,2-dimethyl-propyl]iminomethyl]phenol. High enantioselectivity is dependent on the attachment of an aryl group to the sulfur and was highest, with up to 97% ee, for 2-naphthyl benzyl sulfoxide. Cu-mediated oxidation of substituted aryl benzyl sulfides shows modest steric and electronic effects. ... 

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